cancers

Article Pediatric Suprasellar Germ Cell Tumors: A Clinical and Radiographic Review of Solitary vs. Bifocal Tumors and Its Therapeutic Implications

Darian R. Esfahani 1 , Tord Alden 1,2, Arthur DiPatri 1,2, Guifa Xi 1,2, Stewart Goldman 3 and Tadanori Tomita 1,2,* 1 Division of Pediatric Neurosurgery, Ann & Robert H. Lurie Children’s Hospital, Chicago, IL 60611, USA; [email protected] (D.R.E.); [email protected] (T.A.); [email protected] (A.D.); [email protected] (G.X.) 2 Department of Neurosurgery, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA 3 Division of Hematology, Oncology, Neuro-Oncology & Stem Cell Transplantation, Ann & Robert H. Lurie Children’s Hospital, Chicago, IL 60611, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-312-2274220



Received: 7 August 2020; Accepted: 10 September 2020; Published: 14 September 2020


Simple Summary: Bifocal suprasellar germ cell tumors are a unique type of an uncommon brain tumor in children. Compared to other germ cell tumors in the brain, bifocal tumors are poorly understood and have a bad prognosis. In this paper we explore features that predict which children will have good outcomes and which will not. This is important for the research community because it can help physicians decide what type of radiation treatment is best to treat these children. Our study shows that bifocal tumors have a unique appearance on magnetic resonance imaging (MRI) compared to other germ cell tumors. Children with bifocal tumors are more likely to be male, have tumors that come back sooner, and cause death sooner. We found that children with bifocal tumors likely need a wider radiation field, especially if they have a high-risk tumor type, high-risk appearance on MRI, or tumors spread throughout the nervous system.

Abstract: Suprasellar germ cell tumors (S-GCTs) are rare, presenting in either solitary or multifocal fashion. In this study, we retrospectively examine 22 solitary S-GCTs and 20 bifocal germ cell tumors (GCTs) over a 30-year period and demonstrate clinical, radiographic, and prognostic differences between the two groups with therapeutic implications. Compared to S-GCTs, bifocal tumors were almost exclusively male, exhibited higher rate of metastasis, and had worse rates of progression free and overall survival trending toward significance. We also introduce a novel magnetic resonance (MR) imaging classification of suprasellar GCT into five types: a IIIrd ventricle floor tumor extending dorsally with or without an identifiable pituitary stalk (Type Ia, Ib), ventrally (Type III), in both directions (Type II), small lesions at the IIIrd ventricle floor extending to the stalk (Type IV), and tumor localized in the stalk (Type V). S-GCTs almost uniformly presented as Type I–III, while most bifocal GCTs were Type IV with a larger pineal mass. These differences are significant as bifocal GCTs representing concurrent primaries or subependymal extension may be treated with whole ventricle radiation, while cerebrospinal fluid (CSF)-borne metastases warrant craniospinal irradiation (CSI). Although further study is necessary, we recommend CSI for bifocal GCTs exhibiting high-risk features such as metastasis or non-germinomatous germ cell tumor histology.

Keywords: intracranial germ cell tumor; germinoma; suprasellar tumor; dual germ cell tumor; bifocal germ cell tumor; non-germinoma germ cell tumor; magnetic resonance imaging; radiation; overall survival; progression free survival

Cancers 2020, 12, 2621; doi:10.3390/cancers12092621 www.mdpi.com/journal/cancers Cancers 2020, 12, 2621 2 of 16

1. Introduction Intracranial germ cell tumors (GCTs) are an uncommon malignancy that represent approximately 0.9% of all pediatric tumors, 3.7% of pediatric brain tumors, and 28.7% of germ cell tumors overall [1,2]. However, GCT presentation is very heterogenous, without uniform imaging classification. GCTs occur most often in the pineal (P-GCT) and suprasellar (S-GCT) locations, followed by the basal ganglia (BG-GCT) and rarely at other central nervous system (CNS) sites. GCTs can also arise concurrently in the suprasellar and pineal regions, a distinct pathologic entity described as “bifocal” GCTs [3–6]. Bifocal tumors are especially poorly understood, with few studies analyzing their natural history or comparing outcomes versus solitary GCTs. It is further unclear whether bifocal GCTs represent independent primaries or metastases, with the difference significant for treatment. Independent primaries, for example, are suitable for limited radiation fields, while and metastases warrant full craniospinal irradiation. Per the Central Brain Tumor Registry of the United States, GCTs represent 3.9% of brain tumor patients under the age of 20 [7]. Racial differences exist, with some registries reporting a higher overall incidence of germ cell tumors in patients of Asian descent. The frequency of GCTs in Japan was 16.9% among brain tumor patients under the age of 20, making them the second most common brain tumor type after astrocytoma [8]. According to a Children’s Oncology Group report, the tumor location of 93 intracranial GCTs were P-GCT in 53%, S-GCT in 37%, and bifocal in 5.4%, while a Japanese cooperative study demonstrated P-GCT in 68%, 26 S-GCT in 19%, and bifocal GCT in 13% among 139 GCTs [8]. A comparison study between the Mayo Clinic and Japan National Cancer Center (NCC) demonstrated the frequency of basal ganglia GCTs was higher in the NCC database compared with the Mayo Clinic (8.4% vs. 0%), and bifocal location (S-GCT and P-GCT) was higher at the Mayo Clinic than at the NCC (18.8% vs. 5.8%) [9]. Many authors consider GCTs to be derived from the abnormal migration of germ cells along the midline during embryonal development, where they present along a longitudinal axis from the optic chiasm to the pineal region in the III ventricle. Among GCTs, germinomas of the pineal and suprasellar region are the most common, followed by tumors along the ventricle [3,9–11]. It has been considered that P-GCTs are derived from ectopic cells that migrate to the pineal region and S-GCTs derive from ectopic germ cells that migrate to the hypothalamic infundibulum or neurohypophysis. The pathogenesis of bifocal GCTs is unclear as to whether bifocal GCTs represent tumors developing at both sites simultaneously or are metastases from one site to the other. Takami et al. reported the majority of bifocal or other multifocal tumors (34/35 cases, 97.1%) were germinomas [8]. Literature showing a high rate of tumor seeding (47.8%) in bifocal GCTs and a worse survival in bifocal GCTs supports the metastasis hypothesis [5,6]. Based on clinical and imaging characteristics, Zhang et al. recently suggested a distinction between suprasellar tumors of “true” bifocal GCTs that arise from the neurohypophysis and those of “false” lesions that are metastatic [12]. If the primary lesions of bifocal GCTs are suprasellar, one would suspect they should share similar magnetic resonance (MR) imaging features and initial clinical symptoms as S-GCTs [13]. Currently, there is no consensus of radiation therapy (RT) field for bifocal GCTs. Implicit in treatment choice is the definition of what a bifocal GCT is: if a bifocal GCT represents disseminated disease, it should be treated with full craniospinal irradiation (CSI); if it represents localized disease, treatment with limited fields is more appropriate. This distinction is important for GCT treatment using radiation therapy (RT), as metastatic GCTs likely warrant full craniospinal irradiation (CSI), while localized lesions require only limited field irradiation, which carries less morbidity to the developing nervous system of children [6,14–17]. To better characterize the clinical and radiographic presentation of bifocal GCTs and identify whether they represent independent primaries or metastases, in this study, we retrospectively analyze a population of GCTs, focusing on their clinical presentation, imaging characteristics, and responses to the therapy. Cancers 2020, 12, 2621 3 of 16

2. Results

2.1. Clinical Presentation Eighty-four patients with intracranial GCT were diagnosed and treated during the 30-year study period and retrospectively analyzed. Of these, 42 were solitary pineal GCTs, while the remaining 42 involved the suprasellar region. Of the suprasellar tumors, 22 were confined to the suprasellar region (S-GCT), 16 were also present in the pineal region (bifocal GCT) and four were also present in the basal ganglia (BG-GCT). Among the 42 GCTs involving the suprasellar location, six were managed from 1988 to 1999, and the remaining 36 were managed within the last 20 years. Patient age at diagnosis ranged from six to 18 years of age (mean: 12 years). Children with S-GCT were significantly younger (11.2 years) versus children with bifocal GCTs (13.4 years; p = 0.04). There were 16 females and 26 males. Children in the S-GCT group were much more likely to be female (68.2%), while children in the bifocal GCT group were all male except for one (6.3%) (p < 0.001), with an odds ratio (OR) of 32.71 (confidence interval [CI] 3.51-294.23). The most common presenting symptom was diabetes insipidus (DI). DI was present in all but one S-GCT patient (95.5%), and in 12 of 16 (75%) and three of four (75%) of the bifocal GCT and BG-GCT groups, respectively. The duration of DI before tumor diagnosis ranged from 0 (at the time of tumor detection) to three years; 13 patients had DI for more than one year of duration (median average; 14.5 months among S-GCT, 7.3 months bifocal, and 2.3 months for BG-GCT). Other endocrine dysfunctions were also common at patient presentation. Among the 22 patients with S-GCT, short stature was present in five (22.7%), delayed puberty in three (13.6%), precocious puberty in two (9.1%), excess body weight gain in five (22.7%), and weight loss in two (9.1%). Among the bifocal GCT patients, three (18.8%) had excess weight loss prior to diagnosis. Two patients in the BG-GCT group had endocrine dysfunction, with precocious puberty in one and thyroid and adrenal insufficiency in the other. Visual symptoms were the next most common presenting symptom and were present in nine (40.9%) of the S-GCT and five (31.3%) of the bifocal patients. Three patients (75%) with BG-GCT presented with hemiparesis or involuntary motor movement and then developed DI subsequently. Hydrocephalus was common in the bifocal group and present in 10 (62.5%) of patients, a significantly greater rate than in the S-GCT group (3/22, 13.6%; p = 0.019) with an OR of 10.56 (2.17–51.43). No instances of hydrocephalus were observed in the BG-GCT group.

2.2. Tumor Markers Tumor marker data was available in 36 (85.7%) patients. Fifteen (41.7%) were negative for both markers. Serum alpha fetoprotein (AFP) was elevated in six of 20 (30%) tested patients and ranged from 11.9 to 8,000 ng/mL. Cerebrospinal fluid (CSF) AFP was elevated in four of nine (44.4%) patients and ranged from 2.5 ng/mL to 240 ng/mL. Among 36 patients tested for both CSF and serum beta human chrorionic gonadotropin (β-HCG), 21 (58.3%) demonstrated abnormal values. Serum β-HCG was positive in only eight patients (22.2%) and ranged from 8 IU/L to 312 IU/L. In all but one patient, higher β-HCG titers were noted in the CSF than serum. The range of the β-HCG values in the CSF was 5–10 IU/L in eight patients, 11–50 IU/L in seven patients, and 51–100 IU/L in two patients. The remaining four patients had CSF values higher than 100 IU/L; 120, 131, 341, and 984 IU/L, respectively.

2.3. MR Imaging MR characteristics of suprasellar masses were classified by location and involvement of the pituitary stalk (PS) and pituitary gland (PG) and are described in detail in the Materials and Methods section. A summary by imaging type and location is demonstrated in Table1. The size of the sella turcica was normal in size in all except for three patients of Type II and III, where a mildly enlarged sella turcica was noted. All GCTs in every group demonstrated contrast enhancement. Cancers 2020, 12, 4 of 17 Cancers 2020, 12, 4 of 17 Table 1. Magnetic resonance imaging types. Cancers 2020, 12, 2621 Table 1. Magnetic resonance imaging types. 4 of 16 MR Imaging Type S-GCT Bifocal GCT BG-GCT Total MR Imaging Type S-GCT Bifocal GCT BG-GCT Total Type Ia 3 ++ 2 + 0 5 Type Ia 3 ++ 2 + 0 5 Type Ib Table 1. Magnetic4 + resonance imaging2 + types. 0 6 Type Ib 4 + 2 + 0 6 Type II 7 ** 1 0 8 MR ImagingType II Type S-GCT7 ** Bifocal GCT1 BG-GCT0 Total8 Type III 6 ** 0 2 (L) ++ 8 TypeType IaIII 3 ++6 ** 2 + 0 20 (L) ++ 5 8 Type IV 1+ (L) + 11 (7 L +++; 4 N +++) 0 12 TypeType IbIV 41 (L) + 11 (7 2L ++; 4 N +++) 0 612 TypeType IIV 7 **1 10 2 0 ++ 8 3 Type V 1 0 2 ++ 3 TypeTotal III 6 **22 016 2 (L)4 ++ 8 Total 22+ ++ 16 +++ 4 Type Ia: GlobularType anterior IV III ventricle 1 (L) mass lesio11n (7 with L identifiable; 4 N ) pituitary0 stalk (PS) 12 and pituitary Type Ia: GlobularType anterior V III ventricle 1mass lesion with 0identifiable pituitary 2 ++ stalk (PS)3 and pituitary gland (PG). Type Ib: Globular anterior III ventricle mass lesion without identifiable PS but with gland (PG). Type Ib: Globular anterior III ventricle mass lesion without identifiable PS but with identifiable PG. TypeTotal II: Globular anterior 22 III ventricle 16mass extending to 4 the sella turcica. Type III: identifiable PG. Type II: Globular anterior III ventricle mass extending to the sella turcica. Type III: TypeGlobular Ia: Globular mass extending anterior III from ventricle the massfloor lesionof III withventricle identifiable to sella pituitary turcica stalk. Type (PS) IV: and Small pituitary laminar gland (L) (PG). or Globular mass extending from the floor of III ventricle to sella turcica. Type IV: Small laminar (L) or Typenodular Ib: Globular (N) lesion anterior at III the ventricle floor extendingmass lesion without to upper identifiable PS. Type PS but V: with limited identifiable to PS. PG. Each Type asterisk II: Globular (*) anteriornodular III (N) ventricle lesion mass at the extending floor extendingto the sella turcica. to upper Type PS III:. Type Globular V: masslimited extending to PS. fromEach the asterisk floor of (*) III ventriclerepresents tosella one turcica.patient Type with IV: cavernous Small laminar sinus (L) orinvolvemen nodular (N)t;lesion each atcross the floor(+) represents extending to one upper patient PS. Type with V: represents one patient with cavernous sinus involvement; each cross (+) represents one patient+ with limitedventricular to PS. metastases Each asterisk. Multiple (*) represents asterisks one patient or crosses with cavernousrepresent sinusmultiple involvement; patients. each cross ( ) represents oneventricular patient with metastases ventricular. Multiple metastases. asterisks Multiple or asteriskscrosses orrepresent crosses represent multiple multiple patients. patients. Patients in the S-GCT group skewed toward masses of the anterior III ventricle. Of 22 S-GCTs: Patients in the S-GCT group skewed toward masses of the anterior III ventricle. Of 22 S-GCTs: sevenPatients were Type in the Ia or S-GCT Ib (Figure groups 1 skewed and 2), seven toward were masses Type of II the(Figure anterior 3), and III ventricle.six were Type Of 22 III S-GCTs:(Figure seven were Type Ia or Ib (Figures 1 and 2), seven were Type II (Figure 3), and six were Type III (Figure seven4). These were 20 Type S-GCTs Ia or were Ib (Figures all globular1 and2 ),appearance. seven were TypeIn four II (Figurepatients3), (two and sixeach were of S Type-GCT III Type (Figure II 4and). 4). These 20 S-GCTs were all globular appearance. In four patients (two each of S-GCT Type II and TheseIII), the 20 tumor S-GCTs extended were all laterally globular into appearance. the cavernous In four sinus patients (Figure (two 3C,D; each Figure of S-GCT 4C,D) Type. Each II andof these III), III), the tumor extended laterally into the cavernous sinus (Figure 3C,D; Figure 4C,D). Each of these thepatients tumor presented extended with laterally cranial into thenerve cavernous dysfunction. sinus (FigureThe two3C,D; non Figure-globular4C,D). S-GCTs Each ofwere these small patients and patients presented with cranial nerve dysfunction. The two non-globular S-GCTs were small and presentedconfined to with the cranialPS (Type nerves IV and dysfunction. V). The two non-globular S-GCTs were small and confined to theconfined PS (Types to the IV PS and (Type V). s IV and V).

(A) (B) (C) (D) (A) (B) (C) (D) Figure 1. Type Ia. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with suprasellar Figure 1. Type Ia. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with suprasellar germ cell Typetumor Ia. (S Post-contrast-GCT) and post MR,-contrast sagittal MR, ( ) sagittal and coronal (C) and ( ) coronal views of (D a) patient views of with a patient suprasellar with germ cell tumor (S-GCT)(S-GCT) and post-contrastpost-contrast MR, sagittal ( C) and coronal (D) views of a patientpatient with bifocal GCT. Note an anterior third ventricle tumor with preserved pituitary stalk and gland. bifocal GCT. NoteNote anan anterioranterior thirdthird ventricleventricle tumortumor withwith preservedpreserved pituitarypituitary stalkstalk andand gland.gland.

(A) (B) (C) (D) (E) (A) (B) (C) (D) (E) Figure 2. Type Ib. Post-contrastPost-contrast MR, sagittal ( A) and coronal ( B) views of a patient with S-GCTS-GCT and Figure 2. Type Ib. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with S-GCT and post-contrastpost-contrast MR,MR, sagittal sagittal (C (),C coronal), coronal (D )( andD) and axial axial (E) views (E) views of a patient of a patient with bifocal with GCT.bifocal The GCT. pituitary The post-contrast MR, sagittal (C), coronal (D) and axial (E) views of a patient with bifocal GCT. The stalkpituitary is not stalk visualized is not visualized but the pituitary but the pituitary gland is preserved.gland is preserved. Note the Note subependymal the subependymal infiltrate infiltrate of at the pituitary stalk is not visualized but the pituitary gland is preserved. Note the subependymal infiltrate IIIof at ventricle the III ventricle wall (E). wall (E). of at the III ventricle wall (E).

By contrast, the majority (11 /16, 68.8%) of bifocal GCTs were smaller and Type IV (Figure5). These tumors were accompanied by much larger pineal region tumors. Four bifocal tumors were Type Ia or Type Ib tumors with similarly sized globular masses in the suprasellar and pineal regions. 1 patient had a Type II mass with extension of the tumor directly into the sella turcica.

Cancers 2020, 12, 5 of 17

Cancers 2020, 12, 5 of 17

CancersCancers 20202020,, 1212,, 2621 (A) (B) (C) (D) 55 of 1617 Cancers 2020, 12, 5 of 17 Figure 3. Type II. Post(A-contrast) MR, sagittal(B) (A) and coronal( (CB)) views of a patient(D) with S-GCT. Note the third ventricle tumor extension into the sella turcica. Post-contrast MR, sagittal (C) and coronal Figure(D) views 3. Type of a patientII. Post -withcontrast S-GCT MR, demonstrate sagittal (A) furtherand coronal lateral (B extension) views of to a patientthe cavernous with S -sinus.GCT. Note the third ventricle tumor extension into the sella turcica. Post-contrast MR, sagittal (C) and coronal (D) views of a patient with S-GCT demonstrate further lateral extension to the cavernous sinus.

(A) (B) (C) (D) (A) (B) (C) (D) Figure 3. Type II. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with S-GCT. Note Figure 3. Type II.II. Post-contrastPost-contrast MR, MR, sagittal sagittal (A (A) and) and coronal coronal (B ()B views) views of of a patient a patient with with S-GCT. S-GCT. Note Note the the third ventricle tumor extension into the sella turcica. Post-contrast MR, sagittal (C) and coronal thirdthe third ventricle ventricle tumor tumor extension extension into into the sellathe sella turcica. turcica. Post-contrast Post-contrast MR, MR, sagittal sagit (talC) ( andC) and coronal coronal (D) (D) views of a patient(A with) S-GCT demonstrate(B) further lateral(C )extension to the (cavernousD) sinus. views(D) views of a of patient a patient with with S-GCT S-GCT demonstrate demonstrate further further lateral lateral extension extension to the to cavernousthe cavernous sinus. sinus.

Figure 4. Type III. Post(A)- contrast MR, sagittal(B) (A) and coronal(C (B) ) views of a patient(D) with S-GCT. Note the tumor from the floor of the third ventricle to the sella turcica. Post-contrast MR, sagittal (C) and Figurecoronal 4. (D Type) views III. ofPost a patient-contrast with MR, S- sagittalGCT. Note (A) theand tumor coronal from (B) theviews floor of of a patientthe third with ventricle S-GCT. to Note sella theturcica tumor with from further the floorextension of the into third the ventricle cavernous to sinus.the sella turcica. Post-contrast MR, sagittal (C) and coronal (D) views of a patient with S-GCT. Note the tumor from the floor of the third ventricle to sella turcica with further extension into the cavernous sinus. By contrast, the majority (11/16, 68.8%) of bifocal GCTs were smaller and Type IV (Figure 5).

These tumors were accompanied(A) by much(B) larger pineal region(C) tumors. Four(D) bifocal tumors were By contrast, the majority (11/16, 68.8%) of bifocal GCTs were smaller and Type IV (Figure 5). Type Ia or Type Ib tumors(A) with similarly( sizedB) globular masses(C) in the suprasel(Dlar) and pineal regions. TheseFigure tumors 4.4. Type were III.III. accompanied Post-contrastPost-contrast MR, MR,by sagittal muchsagittal (largerA (A) and) and coronalpineal coronal (regionB ()B views) views tumors. of aof patient a patient Four with withbifocal S-GCT. S-GCT. tumors Note Note the were 1 patientFigure had 4. Typea Type III. IIPost mass-contrast with MR,extension sagittal of (A the) and tumor coronal directly (B) views into of the a patient sella turcica.with S-GCT. Note Typetumorthe Ia ortumor Type from from Ib the tumors the floor floor of with theof the thirdsimilarly third ventricle ventricle sized to globularto the the sella sella masses turcica. turcica. in Post-contrast Post the- contrastsuprasel MR,MR,lar sagittalandsagittal pineal ((CC)) andandregions. the tumor from the floor of the third ventricle to the sella turcica. Post-contrast MR, sagittal (C) and 1 patientcoronal had ((DD a)) Type viewsviews II ofof mass aa patient with with extension S-GCT.S-GCT. NoteNote of the thethe tumor tumor directly from the into floorfloor the of the sella third turcica. ventricle to sella turcicacoronalturcica withwith(D) views furtherfurther of extension extensiona patient with intointo theSthe-GCT. cavernouscavernous Note the sinus.sinus. tumor from the floor of the third ventricle to sella turcica with further extension into the cavernous sinus. By contrast, the majority (11/16, 68.8%) of bifocal GCTs were smaller and Type IV (Figure 5). TheseBy tumors contrast, were the accompanied majority (11/16, by 68.8%)much larger of bifocal pineal GCTs region were tumors. smaller Four and bifocalType IV tumors (Figure were 5). TheseType Ia tumors or Type were Ib tumors accompanied with similarly by much sized larger globular pineal masses region in tumors. the suprasel Fourlar bifocal and pineal tumors regions. were Type Ia or Type Ib tumors with similarly sized globular masses in the suprasellar and pineal regions. 1 patient had a Type II mass with extension of the tumor directly into the sella turcica. 1 patient had a Type II mass with extension of the tumor directly into the sella turcica. (A) (B) (C) (D)

Figure 5. Type IV.(A Post) -contrast MR, sagittal(B) (A) and coronal (BC)) views of a patient with(D) bifocal germ cell tumor (GCT). Note a laminar tumor at the floor of the third ventricle with upper pituitary stalk Figure 5. Type IV. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with bifocal germ Figureinvolvement. 5. Type Post IV. -Postcontrast-contrast MR, MR,sagittal sagittal (C) and (A) coronaland coronal (D) views (B) views of a patientof a patient with with bifocal bifocal GCT germ with cell tumor (GCT). Note a laminar tumor at the floor of the third ventricle with upper pituitary stalk cella nodular tumor tumor(GCT) at. No thete floor a laminar of the tumor third ventricleat the floor with of upperthe third pituitary ventricle stalk with involvement. upper pituitary stalk involvement. Post-contrastPost-contrast MR,MR, sagittalsagittal ((CC)) andand coronalcoronal ( D(D)) views views of of a a patient patient with with bifocal bifocal GCT GCT with with a nodulara nodular tumor tumor at at the the floor floor of of the the third third ventricle ventricle with with upper upper pituitary pituitary stalk stalk involvement. involvement. There were only three Type V tumors (Figure 6), and two of these were BG-GCTs. All four BG- GCTs demonstrated( Aa )prominent PS. Two(B of) these had poorly( Cdefined) hyperintense (D )lesions extending There werewere onlyonly three three Type Type V V tumors tumors (Figure (Figure6), and6), and two two of these of these were were BG-GCTs. BG-GCTs. All four All BG-GCTs four BG- from the BG to corpus(A) callosum, but a prominent(B) PS was present.(C) The other two BG(D)- GCTs were Type demonstratedGCTsFigure demonstrated 5. Type a prominent IV. a Postprominent-contrast PS. Two PS. MR, of Two these sagittal of had these (A poorly) and had coronal definedpoorly (B defined hyperintense) views ofhyperintense a patient lesions with extending lesions bifocal extending germ from the III andFigure were 5. Typemore IV. extensive Post-contrast enhancing MR, sagittal lesions (A ) inand the coronal basal ( Bganglia) views extendingof a patient withthrough bifocal the germ anterior BGfrom to cellthe corpus tumorBG to callosum, (corpusGCT). No callosum, butte a prominentlaminar but tumor a prominent PS wasat the present. floor PS wasof Thethe present. third other ventricle two The BG-GCTs other with two upper were BG -pituitary TypeGCTs III were andstalk Type were cingulatecell tumor gyrus. (GCT ). Note a laminar tumor at the floor of the third ventricle with upper pituitary stalk moreIII andinvolvement. extensive were more enhancing Post extensive-contrast lesions enhancingMR, insagittal the basallesions (C) and ganglia incoronal the extending basal (D) views ganglia through of a patientextending the with anterior through bifocal cingulate GCT the with anterior gyrus. involvement. Post-contrast MR, sagittal (C) and coronal (D) views of a patient with bifocal GCT with cingulatea nodular gyrus. tumor at the floor of the third ventricle with upper pituitary stalk involvement. a nodular tumor at the floor of the third ventricle with upper pituitary stalk involvement. There were only three Type V tumors (Figure 6), and two of these were BG-GCTs. All four BG- GCTsThere demonstrated were only a three prominent Type VPS. tumors Two of (Figure these had 6), andpoorly two defined of these hyperintense were BG-GCTs. lesions All extending four BG- GCTsfrom the demonstrated BG to corpus a prominentcallosum, but PS. aTwo prominent of these P hadS was poorly present. defined The hyperintenseother two BG lesions-GCTs wereextending Type from the BG to corpus callosum, but a prominent PS was present. The other two BG-GCTs were Type III and were more extensive enhancing lesions in the basal ganglia extending through the anterior IIIcingulate and were gyrus. more extensive enhancing(A) lesions in the basal( Bganglia) extending through the anterior cingulate gyrus. Figure 6. Type V. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with S-GCT. Note the (A) (B) thickened pituitary stalk. This seven-year-old girl presented with 18-month history of DI.

Metastases were more common among the bifocal GCT (7/16) and BG-GCT (3/4) groups versus the S-GCT group (4/22), with the combined bifocal and BG GCT patient population significantly more likely to have metastases than their S-GCT counterparts (p = 0.049) with an OR of 4.5 (CI: 1.12i18.13).

All metastases at diagnosis were noted(A) in the lateral ventricle,(B) except for one in the fourth ventricle (A) (B)

Cancers 2020, 12, 6 of 17 Cancers 2020, 12, 6 of 17 Figure 6. Type V. Post-contrast MR, sagittal (A) and coronal (B) views of a patient with S-GCT. Note Figurethe thickened 6. Type pituitary V. Post- contraststalk. This MR, seven sagittal-year (A-old) and girl coronal presented (B) viewswith 18 of-month a patient history with ofS- GCT.DI. Note the thickened pituitary stalk. This seven-year-old girl presented with 18-month history of DI. Metastases were more common among the bifocal GCT (7/16) and BG-GCT (3/4) groups versus the SMetastases-GCT group were (4/22), more with common the combined among bifocal the bifocal and BG GCT GCT (7/16) patient and population BG-GCT (3/4) significantly groups versus more the S-GCT group (4/22), with the combined bifocal and BG GCT patient population significantly more Cancerslikely to2020 have, 12, 2621metastases than their S-GCT counterparts (p = 0.049) with an OR of 4.5 (CI: 1.12i18.13).6 of 16 likelyAll metastases to have metastases at diagnosis than were their noted S-GCT in thecounterparts lateral ventricle (p = 0.049), except with for an one OR in of the 4.5 fourth(CI: 1.12 ventriclei18.13). Alland metastases another in atthe diagnosis subarachnoid were notedspace inover the the lateral cerebellum. ventricle There, except were for noone spinal in the metastases fourth ventricle at the andtime anotheraofnother initial in diagnosis the subarachnoid on spinal spaceMR. over the cerebellum. There were no spinal metastases at the time Exceptof initial for diagnosis the four onpatients spinal who MR. underwent primary surgical resection, MR imaging following adjuvantExcept therapy for the demonstrated four patients wholesion underwent resolution primary in all patients surgical with resection, a preserved MR imaging PS and following either a adjuvantnormal or therapytherapy atrophic demonstrated demonstrated PG (Figure 7). lesion l esionThe resolution PS resolution further in demonstrated allin patientsall patients with anatomic with a preserved a preserved continuity PS and PS during either and a eithersecond normal a- normalorlook atrophic surgery or atrophic PG (Figure (Figure PG 8). (Figure7 ). The 7). PS The further PS further demonstrated demonstrated anatomic anatomic continuity continuity during during second-look second- looksurgery surgery (Figure (Figure8). 8).

(A) (B) (C) (D) (A) (B) (C) (D) Figure 7. Thirteen-year-old male with suspected germinoma with high cerebrospinal fluid (CSF) β- FigureHCG presenting 7. ThirteenThirteen-year-old with-year a -oneold- monthmale male with history with suspected suspected of DI and ger germinoma monocularminoma with visual with high highloss. cerebrospinal cerebrospinalPost-contrast fluid MR, fluid (CSF) sagittal (CSF) β- β HCG(A-HCG) and presenting presentingcoronal ( withB) with views a one a one-month showing-month historyan history enhancing of of DI DI and andmass monocular monocular with Type visual visual II suprasellar loss. loss. Post Post-contrast lesion.-contrast Following MR, MR, sagittal pre- A B (RTA) andchemotherapy, coronalcoronal ((B)) viewstheviews lesion showing showing resolved an an enhancing enhancing on postcontrast mass mass with with MR Type Typesagittal II suprasellarII suprasellar(C) and coronal lesion. lesion. Following (D Following) views. pre-RT Note pre- chemotherapy, the lesion resolved on postcontrast MR sagittal (C) and coronal (D) views. Note normal RTnormal chemotherapy, continuity ofthe the lesion pituitary resolved stalk on and postcontrast atrophic pituitary MR sagittal gland. (C ) and coronal (D) views. Note normalcontinuity continuity of the pituitary of the pituitary stalk and stalk atrophic and atrophic pituitary pituitary gland. gland.

(A) (B) (C) (D) (A) (B) (C) (D) Figure 8. 8. TwelveTwelve-year-old-year-old girl girl with with suprasellar suprasellar tumor tumor with withβ-HCG.β-HCG. Following Following chemotherapy chemotherapy,, the β- FiguretheHCGβ -HCGwas 8. Twelve normalized was normalized,-year,- oldbut girlthere but with was there suprasellar a small was acontrast small tumor contrast-enhancing-enhancing with β-HCG. lesion Following in lesion the left inchemotherapy suprasellar the left suprasellar location, the β- HCGlocationon MR was (sagittal on normalized MR (A (sagittal) and, but coronal (A there) and ( wasB coronal) views). a small ( SurgicalB )contrast views). photographs-enhancing Surgical photographs lesionat second in the-look left at second-looksurgery suprasellar demonstrate location surgery ondemonstratethe MR chiasm (sagittal and the (anA chiasm) atrophicand coronal and but an (continuousB atrophic) views). but Surgical pituitary continuous photographs stalkpituitary (C), which at second stalk is retracted (C-look), which surgery by isa retractedhook demonstrate (D). byThe a thehooklesion chiasm ( Ddemonstrated). The and lesion an atrophic demonstratedno viable but cells. continuous no viable pituitary cells. stalk (C), which is retracted by a hook (D). The lesion demonstrated no viable cells. 2.4. Surgery 2.4. Surgery 2.4. Surgery Of 42 patients, 28 (66.7%) underwent surgical resection or biopsy, 11 underwent a trans-ventricular Of 42 patients, 28 (66.7%) underwent surgical resection or biopsy, 11 underwent a trans- endoscopic approach, nine an open craniotomy, five a transsphenoidal approach, and three a stereotactic ventricularOf 42 patients,endoscopic 28 approach, (66.7%) underwent nine an open surgical craniotomy, resection five or a biopsytranssphenoidal, 11 underwent approach, a trans and- biopsy (Table2). No di fferences were noted between the propensity of different GCT types to ventricularthree a stereotactic endoscopic biopsy approach, (Table 2). nine No an differences open craniotomy, were noted five between a transsphenoidal the propensity approach, of different and undergo surgery. Expectedly, bifocal GCTs were more likely to undergo endoscopic biopsy than threeGCT typesa stereotactic to undergo biopsy surgery. (Table Expectedly, 2). No differences bifocal wereGCTs noted were betweenmore likely the topropensity undergo ofendoscopic different S-GCTs (p = 0.003), while S-GCTs were more likely to undergo craniotomy (p = 0.012). The remaining GCTbiopsy types than to S -undergoGCTs (p surgery.= 0.003), Expectedly,while S-GCTs bifocal were GCTsmore werelikely moreto un likelydergo tocraniotomy undergo endoscopic(p = 0.012). 14 patients had positive tumor markers and were treated with upfront chemotherapy without surgical biopsyThe remaining than S-GCTs 14 patients (p = 0.003), had positive while S tumor-GCTs markers were more and likelywere treatedto undergo with craniotomyupfront chemotherapy (p = 0.012). biopsy. Three of these patients subsequently underwent second-look surgery by craniotomy, and one Thewithout remaining surgical 14 biopsy.patients Three had positive of these tumor patients markers subsequently and were underwenttreated with second upfront-look chemotherapy surgery by by the transsphenoidal approach. withoutcraniotomy, surgical and onebiopsy. by the Three transsph of theseenoidal patients approach. subsequently underwent second-look surgery by craniotomy, and one by the transsphenoidal approach.

Table 2. Surgery. Approach S-GCT Bifocal GCT BG-GCT Total No biopsy 8 (2) 5 (2) 1 14 Endoscopic 2 9 0 11 Craniotomy 8 0 1 9 Transsphenoidal 4 1 0 5 Stereotactic 0 1 2 3 Total 22 16 4 42 The number in parenthesis (x) represents the number of patients undergoing second-look surgery after initial treatment with radiation or chemotherapy. Cancers 2020, 12, 2621 7 of 16

2.5. Pathology Pathology results are illustrated in Table3. Diagnosed (24) and suspected (nine) germinomas were the most common in the series, constituting 33 of 42 (78.6%) of this cohort. All suspected germinomas had elevated β-HCG in the CSF and demonstrated a complete response to neoadjuvant chemotherapy. Non-germinomatous germ cell tumors (NGGCTs) were most common in the S-GCT group (7/22, 31.8%), were uncommon in the bifocal group (2/16, 12.5%), and absent among BG-GCTs, although these differences did not reach significance. Of the nine NGGCTs, five were AFP producing and three had high β-HCG, which set at a threshold of greater than 100 IU/L. One patient had both high AFP (222 ng/mL in serum and 90 ng/mL in CSF) and β-HCG (312.4 IU/L in serum and 984 IU/L in CSF). While almost all patients with a β-HCG greater than 100 IU/L were NGGCTs, this was not universal, with a single biopsy-confirmed germinoma having a CSF level of 180 IU/L.

Table 3. Pathology.

Pathology S-GCT Bifocal GCT BG-GCT Total Germinoma (diagnosed) 10 11 3 24 Germinoma (suspected) 5 3 1 9 NGGCT 7 2 9 Alpha fetoprotein (AFP) 3 2 β-HCG >100 IU/L 3 AFP + β-HCG >100 IU/L 1 Total 22 16 4 Four of the seven suprasellar non-germinomatous germ cell tumors (NGGCTs) had a mature teratoma component. Two mature teratomas were identified surgically before adjuvant treatment, and two during the second look surgery. Of the two bifocal NGGCTs, the second look surgery showed no viable tumors.

2.6. Adjuvant Therapy Neoadjuvant chemotherapy prior to RT was applied to all but one patient. Most patients were enrolled in Children’s Oncology Group (COG) germ cell protocol ACNS0122, 0232, and most recently in ACNS 1123. 1 patient had on COG ACNS0232 randomization, and received only RT. All patients subsequently received RT. Radiation fields are described in Table4. Whole ventricle (WV) with focal boost was applied to 17 patients, all with germinomas and three with evidence of intra-ventricular metastases. Craniospinal irradiation (CSI) with tumor bed boost was applied to 19 patients including seven NGGCTs; among them, 10 demonstrated intraventricular metastases. Intraventricular metastases were significantly more common among patients undergoing CSI (52.6%) than those undergoing WV therapy (17.6%; p = 0.041), with an OR of 5.19 (1.11–24.14). The remaining five patients had limited field radiation with intensity modulated RT. 1 patient treated very early in the study had whole brain (WB) radiation.

Table 4. Radiation therapy field and intraventricular metastases.

Radiation Therapy S-GCT Bifocal GCT BG-GCT Total Germinoma NGGCT Germinoma NGGCT Germinoma Whole ventricle 9 (2) 8 (1) 17 (3) CSI 1 (1) 6 7 (5) 1 (1) 4 (3) 19 (10) Involved field 4 1 (1) 5 (1) Whole brain 1 1 Total 15 (3) 7 (1) 15 (6) 1 (1) 4 (3) 42 (14) The number in parenthesis (x) represents the number of patients with intraventricular metastases before therapy. CSI: craniospinal irradiation. Cancers 2020, 12, 8 of 17

Table 4. Radiation therapy field and intraventricular metastases.

Radiation Therapy S-GCT Bifocal GCT BG-GCT Total Germinoma NGGCT Germinoma NGGCT Germinoma Whole ventricle 9 (2) 8 (1) 17 (3) Cancers 2020, 12, 2621 8 of 16 CSI 1 (1) 6 7 (5) 1 (1) 4 (3) 19 (10) Involved field 4 1 (1) 5 (1) Whole brain 1 1 2.7. Clinical Outcomesq456Total 15 (3) 7 (1) 15 (6) 1 (1) 4 (3) 42 (14) All patientsThe hadnumber initial in parenthesis response (x) torepresents pre-RT the chemotherapy number of patients with with totalintraventricular or near metastases total resolution except before therapy. CSI: craniospinal irradiation. for four patients with NGGCT who underwent a second look surgery for resection of a residual lesion. The2.7. second Clinical lookOutcomes surgeryq456 demonstrated a mature teratoma in two S-GCT patients, one of which was removedAll by patients craniotomy had initial and response another to bypre- aRT transsphenoidal chemotherapy with approach. total or near The total other resolution two patients demonstratedexcept only for four scar patients tissue withwithout NGGCT viable whotumors. underwent a second look surgery for resection of a Progressionresidual lesion. free The and second overall look survival surgery demonstrated were the a two mature clinical teratoma outcomes in two S-GCT analyzed patients, one in this study. of which was removed by craniotomy and another by a transsphenoidal approach. The other two Children inpatients the S-GCT, demonstrated bifocal, only and scar BG-GCT tissue without groups viable were tumors. followed for a mean of 9.5, 6.6, and 5.7 years, respectively. AmongProgression patients free and who overall survived survival untilwere the the two end clinical of the outcomes study period,analyzed thein this suprasellar study. group was followedChildren for in a the mean S-GCT, of bifocal, 9.0 years, and BG the-GCT bifocal groups group were foll forowed 7.8 years,for a mean and of the9.5, 6.6, BG-GCT and 5.7 group for 5.7 years,years, a diff erencerespectively. that Among was not patients significant who survived (p = 0.23).until the end of the study period, the suprasellar group was followed for a mean of 9.0 years, the bifocal group for 7.8 years, and the BG-GCT group Kaplan–Meierfor 5.7 years, plotsa difference for progression that was not significant free and (p overall = 0.23). survival are illustrated in Figure9. At the end of the studyKaplan period,–Meier plots 18/22 for (81.8%)progression patients free and inoverall the survival S-GCT are group, illustrated 11/ 16in Figure (68.8%) 9. At in the the bifocal, and 4/4 (100%)end of ofthe thestudy BG-GCT period, 18/22 group (81.8%) did patients not demonstrate in the S-GCT tumorgroup, 11/16 recurrence (68.8%) in or the progression, bifocal, and although this did not4/4 achieve(100%) of significancethe BG-GCT group (p = did0.29). not demonstrate (Figure9A). tumor By recurrence the end ofor progression, the study period,although 21this/ 22 (95.4%) did not achieve significance (p = 0.29). (Figure 9A). By the end of the study period, 21/22 (95.4%) patients inpatients the suprasellar in the suprasellar group group survived, survived, versus versus 12/16 12 /(75%)16 (75%) in the bifocal in the and bifocal 4/4 (100%) and in 4 the/4 (100%)BG- in the BG-GCT groups,GCT groups, a trend a trend toward toward significancesignificance (p = (p 0.09)= 0.09) (Figure (Figure 9B). 9B).

100%

80%

60% p = 0.29

Free Survival Free - 40%

S-GCT 20%

Bifocal Progression BG-GCT 0% 0 40 80 120 160 200 240

Months

Cancers 2020, 12, 9 of 17 (A) 100%

80%

p = 0.09 60%

40% S-GCT Overall Survival Overall 20% Bifocal

BG-GCT 0% 0 40 80 120 160 200 240

Months

(B)

FigureFigure 9. Progression 9. Progression free free and and overall survival survival.. Kaplan Kaplan–Meier–Meier survival survivalcurves illustrating curves progression illustrating progression free survival (A) and overall survival (B) for patients with S-GCT, bifocal, and basal ganglia (BG)- free survival (A) and overall survival (B) for patients with S-GCT, bifocal, and basal ganglia (BG)-GCT. GCT. Children with bifocal tumors trended toward worse overall survival versus the other groups (p Children= 0.09). with bifocal tumors trended toward worse overall survival versus the other groups (p = 0.09).

Table 5 illustrates the relationships between tumor histology, applied radiation fields, and tumor recurrence. Nine patients had recurrence during the follow-up period: four S-GCTs, five bifocal GCTs, and no BG-GCTs.

Table 5. Radiation therapy field and recurrences.

Radiation Therapy S-GCT Bifocal GCT BG-GCT Total Germinoma NGGCT Germinoma NGGCT Germinoma Whole ventricle 9 (1) 8 (2) 17 (3) CSI 1 6 (2) 6 (1) 2 (2) 4 19 (5) Involved field 4 1 (1) 5 (1) Whole brain 1 1 Total 15 (1) 7 (3) 14 (3) 2 (2) 4 42 (9) The number in parenthesis (x) represents the number of patients with recurrence.

Germinomas had excellent responses to chemo-radiotherapy with a recurrence rate around 10%, whereas NGGCT were much higher, at 50%. Of the four S-GCTs that recurred, three were NGGCT and one was a germinoma. The latter showed a single spinal metastasis two years after WV irradiation. One patient with NGGCT with high AFP and β-HCG developed recurrence 11 years later with an intrasellar mature teratoma. Another patient with NGGCT (high β-HCG) developed suprasellar and subarachnoid dissemination 18 months after limited field RT; she died of tumor six years after the diagnosis. The other patient with NGGCT (high AFP) had a local recurrence seven years after CSI RT with a histologically confirmed germinoma. Five bifocal GCTs recurred: three were germinomas and two were NGGCTs. Three were treated with CSI RT, and two germinomas received WV RT.

Cancers 2020, 12, 2621 9 of 16

Table5 illustrates the relationships between tumor histology, applied radiation fields, and tumor recurrence. Nine patients had recurrence during the follow-up period: four S-GCTs, five bifocal GCTs, and no BG-GCTs.

Table 5. Radiation therapy field and recurrences.

Radiation Therapy S-GCT Bifocal GCT BG-GCT Total Germinoma NGGCT Germinoma NGGCT Germinoma Whole ventricle 9 (1) 8 (2) 17 (3) CSI 1 6 (2) 6 (1) 2 (2) 4 19 (5) Involved field 4 1 (1) 5 (1) Whole brain 1 1 Total 15 (1) 7 (3) 14 (3) 2 (2) 4 42 (9) The number in parenthesis (x) represents the number of patients with recurrence.

Germinomas had excellent responses to chemo-radiotherapy with a recurrence rate around 10%, whereas NGGCT were much higher, at 50%. Of the four S-GCTs that recurred, three were NGGCT and one was a germinoma. The latter showed a single spinal metastasis two years after WV irradiation. One patient with NGGCT with high AFP and β-HCG developed recurrence 11 years later with an intrasellar mature teratoma. Another patient with NGGCT (high β-HCG) developed suprasellar and subarachnoid dissemination 18 months after limited field RT; she died of tumor six years after the diagnosis. The other patient with NGGCT (high AFP) had a local recurrence seven years after CSI RT with a histologically confirmed germinoma. Five bifocal GCTs recurred: three were germinomas and two were NGGCTs. Three were treated with CSI RT, and two germinomas received WV RT.

3. Discussion

3.1. Pathogenesis of Intracranial GCT The pathogenesis of intracranial GCTs remains poorly understood. Teilum proposed that germ cell progenitors mis-migrate during early embryogenesis, become trapped in the midline axis, and become a source of GCTs [18]. The mechanism of this mis-migration remains unknown. All GCTs develop from a common precursor, a totipotent primordial germ cell capable of embryonic and extraembryonic differentiation irrespective of site [19]. However, Sano theorized that the only “true” GCT is the germinoma, while the others, NGGCT, are not from the primordial germ cell but should be regarded as enfolded-cell-derived dysembryogenetic cells [20]. The presence of GCT in specific diencephalic loci suggests that local factors are important in either attracting germ cells to these sites or altering normal patterns of development [21]. Jennings et al. theorized that the neuroendocrine events of puberty are an “activating” influence in the malignant expression of embryonal tumors due to their specificity of origin within the positive (suprasellar cistern–suprachiasmatic nucleus) and negative (pineal) regulatory centers for gonadotropin secretion within the diencephalon [21]. Stem-cell-related proteins (C-KIT, OCT-3/4 (POU5F1), AP-2γ (TFAP2C), and NANOG) and developmentally regulated germ-cell-specific proteins are highly expressed in CNS GCTs [22]. The expression of genes associated with embryonic stem cell pluripotency indicates that CNS GCTs are derived from cells that retain, at least partially, an embryonic stem-cell-like phenotype, which is a hallmark of primordial germ cells [22]. These GCTs arise from the transformation of endogenous brain cells and likely originate from neural progenitors rather than mis-migrated germ cell progenitors. Neural stem cells acquire or maintain OCT4 expression to form a cell with pluripotent features. Gene activation of OCT4 by demethylation, together with the local high hormonal activity such as IGFs and GnRH, may be important in the transformation of cells in the ventral midline brain toward tumor formation [23]. Cancers 2020, 12, 2621 10 of 16

3.2. Suprasellar GCT Based on our MR classification, isolated S-GCTs predominately either arise from the III ventricle floor dorsally to the III ventricle cavity (Type I), from the floor ventrally to the suprasellar/sellar location (Type III) or both directions (Type II). A minority are present at the median eminence to the upper PS (Type IV) or only at the PS (Type V). None of our patients had a localized GCT within the sella turcica at the neurohypophysis at tumor diagnosis. Based on this observation, it appears that the tuber cinereum and the median eminence through the pituitary stalk are most likely the site for the origin of S-GCTs. Nearly all S-GCTs present with DI, which may be latent and last for several years, as demonstrated in our series and others [12,23]. The presence of DI among intracranial GCTs strongly indicates suprasellar disease, and endoscopic visualization is often more sensitive to confirm this than MR findings [24]. In addition, patients with S-GCT often present with other endocrine disorders indicative of hypothalamic dysfunction such as excess changes in body weight and precocious or delayed puberty. Of interest, following successful therapy, the pituitary stalk was noted to be in anatomic continuity from the floor of the III ventricle to the normal or atrophic pituitary gland in each group. It is a common finding that the PS reappears or normalizes after treatment even if not initially visualized or enlarged from tumor involvement on pre-treatment MR. This finding suggests GCT cells infiltrate the stalk rather than replace cells of the hypothalamoneurohypophyseal axis (HNA).

3.2.1. Bifocal Germ Cell Tumors Bifocal intracranial GCTs are a distinct, unique presentation of intracranial germ cell tumors that, while described in the literature, remain poorly understood [3–6]. Attributable to their dual nature, the epidemiology of bifocal GCTs carries features common to both suprasellar and pineal region GCTs, a finding also exhibited in our series. The incidence of bifocal GCTs are reported 5–25% among intracranial GCTs [4,6,11].

3.2.2. Demographics The mean age of bifocal tumors in this cohort was 13.3 years of age, significantly older than the suprasellar group. While the overall cohort age was similar to pediatric databases and studies [1,5], the reason the bifocal GCT group skewed older is not clear. Most of bifocal GCTs are germinomas which tend to present at an older age than the other histology groups [8]. Another hypothesis is that the bifocal group may represent a more advanced form of the disease, with the additional time allowing for either the tumor cells to propagate from one site to the second or new, spontaneous lesions to arise [5,12]. Significant sex differences exist among intracranial GCTs, which are anywhere from 1.8 to 3.3 times more prevalent among males than females [1,25]. This difference varies by location, however, with a recent SEER registry study demonstrating sellar region GCTs proportionally half as common among males (13%) versus females (25%), while pineal region GCTs are markedly more frequent in males (61%) than females (16%) [25]. Other registry studies have found similar findings, with GCTs of the pineal gland 14–21 times more common among males than females, while the ratio was much lower for GCTs located elsewhere [9,26]. This study supports these earlier findings, with the suprasellar group 68% female and the bifocal GCT group almost exclusively male. The finding that the bifocal GCT group exhibited a sex distribution pattern closer to the pineal group is potentially revealing; this supports that bifocal GCTs either arise originally from pineal masses that spread to the suprasellar region or, conversely, rarely occur in females. One mechanism for the rarity of pineal GCTs in females is that GCTs are specific to the positive (suprasellar hypothalamic nucleus) and negative (pineal) regulatory centers for gonadotropin secretion within the diencephalon [21]. Regardless, this finding suggests that if bifocal tumors represent the spread of the GCTs from one area to the next, it most often occurs from the pineal region to the suprasellar region, and not the reverse. Cancers 2020, 12, 2621 11 of 16

If suprasellar GCTs were to spread to the pineal gland, a much greater proportion of female patients in the bifocal group would be expected.

3.2.3. Symptoms Among the bifocal GCT group, 12 (75%) patients initially presented with DI. Of 5 Type I and II bifocal GCTs, all had DI, with one at presentation and four within 18 months of diagnosis. Of the 11 patients with Type IV bifocal GCTs, seven (64%) presented with DI, with three at the time of diagnosis, two within one month, and two within three years. Bifocal GCTs of the patients who presented with early DI, neuroendocrine dysfunction, or visual impairment are suspicious for primary suprasellar lesions rather than secondary. Conversely, those that presented with hydrocephalus from a pineal mass or developed delayed DI are more likely to represent secondary suprasellar lesions. Thus, there are two distinct presentations among bifocal GCT, one potentially of suprasellar origin and another of pineal origin, based upon clinical symptomatology. Based on our MR classifications, 7/9 (77.8%) pineal-primary and 4/7 (57.1%) suprasellar-primary tumors were Type IV, and the rest were either Type I subtype.

3.2.4. Pathomechanisms of Bifocality Two potential mechanisms explain the pathophysiology of bifocal GCTs: 1) true multicentric synchronous occurrence in the suprasellar and pineal regions or 2) the spread from one site to the other. The mechanism of GCT “spread” from one site to the other remains unclear. GCTs disseminate both by infiltration into the adjacent hypothalamus and via the ventricular and subarachnoid pathways [21]. IfCancers CSF-borne 2020, 12, metastasis of cells is the mechanism, one would expect a higher incidence of lesions12 of 17 in the other ventricles or subarachnoid spaces. In our cohort, half (10/20) of multifocal GCTs had intraventricularin the suprasellar seeding or the on pineal MR withregion two by positive CSF-borne cytology metastases results. is The challenging preferential to localizationexplain, but in may the suprasellarrepresent relatively or the pineal stagnant region CSF by flow CSF-borne within metastases the III ventricle is challenging at the infundibular to explain, butrecess may and represent pineal- relativelysuprapineal stagnant recess, CSFas shown flow within by Holmlund the III ventricle et al. [27]. at theWe infundibularpostulate stagnant recess CSF and flow, pineal-suprapineal compounded recess,with vascularity as shown byat Holmlundthe median et eminence al. [27]. We and postulate pineal gland stagnant as circumventricular CSF flow, compounded organs with may vascularity provide atfavorable the median nesting eminence sites and for pineal GCTs. glandAnother as circumventricular mechanism of GCT organs spread may provide is direct favorable subependymal nesting sitesextension for GCTs. along Another the floor mechanism or walls of ofthe GCT III ventricle. spread is It direct has been subependymal suggested extensionthat the tumor along develops the floor oreither walls multicentrically of the III ventricle. or by It subependymal has been suggested laminar that infiltration the tumor around develops the either third multicentrically ventricle when orit byoccurs subependymal in multiple laminar midline infiltration sites, rather around than the by third subarachnoid ventricle when or CSF it occurs pathway in multiple metastasis midline [28]. sites,However, rather radiographic than by subarachnoid evidence orof CSFsubependymal pathway metastasis infiltration [28 ].between However, the radiographic suprasellar evidenceand pineal of subependymallesions is rare on infiltration MR (Figure between 2E). the suprasellar and pineal lesions is rare on MR (Figure2E). Rarely, bifocalitybifocality is notednoted with germinomasgerminomas occurring in the suprasellar and basal ganglia ganglia [29]. [29]. In our our cohort, cohort, the the incidence incidence of of radiographic radiographic intraventricular intraventricular disseminations disseminations was was high high among among the BG the- BG-GCTGCT group. group. However, However, there there is a possibility is a possibility of direct of direct subependymal subependymal tumor tumor extension extension along alongthe third the thirdventricle ventricle wall (hypothalamus) wall (hypothalamus) (Figure (Figure 10). 10).

(A) (B) (C)

Figure 10. 10.A A 10-year-old 10-year-old boy boy with with a month a month history history of progressive of progressive right sided right hemiparesis sided hemiparesis and headaches. and Onheadaches. admission On he admission was noted he panhypopituitarism was noted panhypopituitarism including DI. including Post-contrast DI. Post MR,-contrast axial (A MR,), coronal axial ( (AB),), andcoronal sagittal (B), and (C) imagessagittal showing(C) images para-ependymal showing para-ependymal enhancements enhancements with Type III with suprasellar Type III suprasellar lesion. lesion.

The relationship between bifocal GCT and ventricular metastases is supported by our study, with half of bifocal GCTs presenting with metastasis, four and a half times greater odds than lesions confined to the suprasellar region. Expectedly, the bifocal group trended toward worse overall survival (Figure 9b), likely for this reason. Previous literature has reported a similar rate of metastasis, with a paper by Weksberg et al. showing 25/55 (45%) patients among bifocal lesions exhibiting ventricular or CSF positive disease, similar to our rate of 50% among the multifocal GCT group [6]. Weksberg et al. further reported a worse five-year progression free survival (80%) versus patients without evidence of metastasis (95%), similar to our cohort. The presence of tumor seeding in about half of patients and worse survival in bifocal GCTs supports the metastasis hypothesis [5,6]. Recent work by Zhang et al. has suggested that close review of clinical and imaging features can distinguish between “true” and “false” bifocal GCTs [12]. “True” bifocal tumors indicate a dual- primary, while the “false” bifocal is a metastasis from the pineal GCT to the floor of the III ventricle. They reported from an MRI analysis of 95 S-GCT in the literature that all neurohypophyseal germinomas exhibit thickening of the entire PS including the inferior pituitary stalk, which are the cardinal signs of “true” bifocal GCTs. “True” bifocal GCTs further demonstrated a larger extension of the tumor into the HNA, and a figure-eight or bottle-plug-shaped HNA. These tumors universally presented with DI. Zhang et al. concluded that primary germinomas that originated from the neurohypophysis grow toward the hypothalamus and have thickening of the entire PS including a thickened inferior PS. Conversely, in “false” bifocal GCTs, suprasellar lesions represent metastatic lesions to the III ventricle floor that grow toward the PS. On MR, they commonly exhibit a normal, irregular, or inverted cone shaped HNA and normal appearing PS [12], resembling Type IV tumors in our series.

Cancers 2020, 12, 2621 12 of 16

The relationship between bifocal GCT and ventricular metastases is supported by our study, with half of bifocal GCTs presenting with metastasis, four and a half times greater odds than lesions confined to the suprasellar region. Expectedly, the bifocal group trended toward worse overall survival (Figure9b), likely for this reason. Previous literature has reported a similar rate of metastasis, with a paper by Weksberg et al. showing 25/55 (45%) patients among bifocal lesions exhibiting ventricular or CSF positive disease, similar to our rate of 50% among the multifocal GCT group [6]. Weksberg et al. further reported a worse five-year progression free survival (80%) versus patients without evidence of metastasis (95%), similar to our cohort. The presence of tumor seeding in about half of patients and worse survival in bifocal GCTs supports the metastasis hypothesis [5,6]. Recent work by Zhang et al. has suggested that close review of clinical and imaging features can distinguish between “true” and “false” bifocal GCTs [12]. “True” bifocal tumors indicate a dual-primary, while the “false” bifocal is a metastasis from the pineal GCT to the floor of the III ventricle. They reported from an MRI analysis of 95 S-GCT in the literature that all neurohypophyseal germinomas exhibit thickening of the entire PS including the inferior pituitary stalk, which are the cardinal signs of “true” bifocal GCTs. “True” bifocal GCTs further demonstrated a larger extension of the tumor into the HNA, and a figure-eight or bottle-plug-shaped HNA. These tumors universally presented with DI. Zhang et al. concluded that primary germinomas that originated from the neurohypophysis grow toward the hypothalamus and have thickening of the entire PS including a thickened inferior PS. Conversely, in “false” bifocal GCTs, suprasellar lesions represent metastatic lesions to the III ventricle floor that grow toward the PS. On MR, they commonly exhibit a normal, irregular, or inverted cone shaped HNA and normal appearing PS [12], resembling Type IV tumors in our series.

3.2.5. Implications of Bifocality for Irradiation The natural course of bifocal germinomas is not significantly different from localized intracranial germinoma, which can be controlled with an extended focal radiotherapy field [6]. Whether or not bifocal GCTs represent metastatic lesions carries important implications for treatment, however. If bifocal lesions are considered metastases, empiric treatment with craniospinal irradiation (CSI) is indicated; if not, CSI should be reserved as a salvage therapy when local radiotherapy (RT) and chemotherapy fail [6]. A well-cited multicenter study by Calaminus et al. identified that patients with localized germinomas exhibited higher rates of treatment relapse with chemotherapy and focal RT alone versus CSI, although inclusion of the ventricles in the RT may make local therapy more effective [14]. Other studies have demonstrated high risk of late GCT recurrence with focal RT and chemotherapy alone, although CSI was found to be effective as a salvage therapy [15]. Zhang et al. recommended that since “false” bifocal GCTs represent metastasis, they warrant CSI, while “true” GCTs in the absence of other metastases can be treated with limited radiotherapy alone [12]. CSI in bifocal GCTs has been controversial, with some authors advocating initial CSI only in patients with disseminated disease, limiting RT fields until local RT fails [6]. More recent studies, however, have supported the bifocal metastatic hypothesis, pointing towards the high failure rate of local RT fields in localized disease and low toxicity of modern CSI to justify CSI in patients with bifocal disease [30–32]. Cuccia and Alderete defined bifocal GCT as a group of GCTs that lacked seeding between tumors or to distant sites and suggested that spinal radiotherapy was unnecessary [3]. Weksberg et al. divided bifocal GCTs into two groups: tumors without metastases (group 1) and tumors with metastases to other locations (group 2) [6]. They found that limited radiotherapy for group 1 tumors was associated with spinal failures. Another study by Phi et al. advocated that bifocal GCTs likely result from metastatic spread of suprasellar or pineal GCTs because nearly half of their patients with bifocal lesions presented with gross seeding or positive CSF cytology. Thus, they recommended CSI [5]. Cancers 2020, 12, 2621 13 of 16

4. Materials and Methods

4.1. Data Acquisition A consecutive review of all patients with intracranial GCTs managed at a tertiary academic pediatric neurosurgery service over a 30-year period (1988–2018) was performed. GCTs were defined as histologically confirmed tumors undergoing biopsy/resection or tumors that had both radiographic features and positive serum and/or cerebrospinal fluid (CSF) tumor markers indicative of a GCT. Project approval was obtained through the hospital institutional review board (study# 2005-12692). Detailed clinical data on GCT patients were obtained from the data bank of Falk Brain Tumor Center at the Ann & Robert Lurie Children’s Hospital of Chicago, IL, USA. Demographics, including age at presentation and sex were documented for each patient, as well as symptoms, including hydrocephalus, abnormal endocrine function with particular attention to diabetes insipidus (DI), and visual deficits. Radiographic images, pathology reports, applied therapies, and treatment responses were also reviewed.

4.2. MR Classification Pre-treatment MRI features for each patient were reviewed focusing on tumor location, extension and evidence of dissemination. All tumors involving the suprasellar location were included in this study. Tumors were classified into three groups: (1) solitary suprasellar lesions (S-GCT), (2) concurrent lesions in the suprasellar and pineal regions (bifocal GCTs), and (3) concurrent lesions in the suprasellar region and basal ganglia (BG-GCT). MR images were evaluated to analyze the characteristics of suprasellar lesions based on their location (III ventricle cavity, floor, suprasellar, parasellar and intrasellar) and appearance of pituitary stalk (PS) and pituitary gland (PG). The plane connecting the chiasm and mammillary body was considered to be the floor of the III ventricle. PS thickening was defined as 3.0 mm and greater in diameter or the presence of an abnormal nodule along the stalk [33]. Based on MR imaging findings, suprasellar lesions of each group (S-GCT, bifocal GCT, and BG-GCT) were classified based on the MR findings into five types as follows:

Type Ia: Globular anterior III ventricle lesion with identifiable PS and PG (Figure1); Type Ib: Globular anterior III ventricle lesion without identifiable PS but with identifiable PG (Figure2); Type II: Globular anterior III ventricle mass extending to the sella turcica (Figure3); Type III: Globular mass extending from the floor of III ventricle to sella turcica (Figure4); Type IV: Small laminar (L) or nodular (N) lesion at the floor of III ventricle extending to upper PS (Figure5); Type V: Limited to the PS (Figure6).

4.3. Pathologic Classification Metastases were defined as the presence of tumor in the ventricles or subarachnoid spaces outside the suprasellar or pineal regions on initial imaging or having positive CSF cytology for a GCT. MR findings before both RT/chemotherapy and afterward were recorded to evaluate treatment response and the appearance of the pituitary stalk and gland in each patient. The pathology of each case was classified based upon the surgical specimen, CSF, and serum tumor markers. When the surgical biopsy specimen was not available for histological verification, the pathology was suspected based on tumor markers and responses to adjuvant therapy. GCTs were divided into two groups: germinoma and non-germinomatous GCTs (NGGCT). The presence of serum and CSF alpha fetoprotein (AFP) and beta HCG (β-HCG) were documented. AFP values of serum <10 ng/mL and CSF < 2 ng/mL were considered within the normal range. Greater AFP parameters were considered NGGCT with embryonal carcinoma or endodermal sinus tumor components. Serum and CSF β-HCG values above the reference range were considered abnormal. Tumors with β-HCG Cancers 2020, 12, 2621 14 of 16 values >100 IU/L were considered to be NGGCT, while those above the reference age but below this value were suggestive of germinoma. Adjuvant treatments (radiation and chemotherapy) were also documented for each patient. All patients were evaluated with MR during the chemotherapy and post-radiation periods. Progression-free survival (PFS) was defined as the time between clinical diagnosis and tumor growth on follow-up imaging, death, or the last clinical follow-up, whichever came first. Overall survival (OS) was defined as the time between clinical diagnosis and death, or, for survivors, the last clinical follow-up.

4.4. Statistical Analysis Two-tailed Student’s t tests and analysis of variance (ANOVA) tests were performed to determine differences in numerical variables between the S-GCT, bifocal, and BG-GCT groups. Pearson’s chi-squared, and, if significant, Fisher’s exact tests were performed to calculate differences between categorical variables. Logrank (Mantel–Cox) tests were performed to calculate differences in overall and progression free survival. Statistically significant values were identified with a P less than 0.05, and confidence intervals defined at 95%. All statistics were performed using Statistical Analysis System (SAS) (SAS Institute, Inc., Cary, NC, USA), and Microsoft Excel (Microsoft, Redmond, WA, USA).

5. Conclusions In this study, we explore a large cohort of patients with solitary suprasellar (S-GCT) and bifocal GCTs and demonstrate several important differences between the two groups. There is a striking difference in sexual distributions between solitary S-GCTs, which demonstrated a female predominance, and the other groups, which were almost exclusively male. As both solitary pineal GCTs and bifocal tumors both demonstrate similar male predominance, this suggests bifocal tumors are likely of pineal origin. A trend toward worse PFS and OS and higher rate of CSF seeding in the bifocal group is also notable, suggesting bifocal tumors represent either later-presenting disease or metastases. We further introduce a novel MR classification that demonstrates a different radiologic appearance between isolated suprasellar tumors and suprasellar masses with additional lesions in the pineal region (bifocal tumors). S-GCTs almost uniformly present at the floor of the III ventricle and extend dorsally with or without an identifiable PS (Types Ia and Ib), ventrally (Type III) or in both directions (Type II). Small lesions limited to the anterior III ventricle floor or the PS are rare among S-GCTs. Conversely, the majority of bifocal GCTs show a small nodular or laminar lesion at the floor of the III ventricle extending to the upper PS (Type IV) with much larger pineal mass. Taken together, a distinct radiographic appearance, marked male predominance, and much higher rate of metastases among the bifocal group suggests that a majority of bifocal GCTs represent metastases from the pineal to the suprasellar region. Exceptions may be present in cases with prolonged DI, the universal symptom for solitary GCTs, smaller pineal masses without hydrocephalus, and suprasellar lesions with BG-GCTs, which may represent either ventricular dissemination or peri-ependymal extension through the wall of the IIIrd ventricle. The current study cannot definitively conclude whether bifocal GCTs represent concurrent dual primaries, subependymal extension from the pineal region to the suprasellar, or CSF-borne metastases. Radiation fields may be reduced in the former two, but the latter requires an extended radiation field. Localized S-GCTs are treated with WV RT, but in high risk groups such as metastatic disease or NGGCT, CSI is justified. For bifocal GCTs, WV is as effective as CSI if there are no signs of metastatic lesions. It may also be reasonable to have a higher level of concern for bifocal lesions that carry a distinctive MR appearance (Type IV) more suggestive of metastasis than those more common to S-GCTs (Types I-III). However, these recommendations should be tentative, and a larger prospective multicenter study is necessary to draw more definitive conclusions. The primary limitation of this study is its small sample size and its retrospective nature. Although comparable to other studies of bifocal lesions in the literature [5,6,12], it is possible that many Cancers 2020, 12, 2621 15 of 16 of the findings in this study that trended towards significance, including progression free and overall survival, may have been significant if additional data were available.

Author Contributions: Conception and design: T.T. and D.R.E.: Acquisition of data: T.T., D.R.E., A.D., T.A., and S.G.: Analysis and interpretation of data: D.R.E., G.X., and T.T.: Drafting the article: T.T. and D.R.E. All authors have read and agreed to the published version of the manuscript. Funding: This research was partly supported by Yeager Professorship of Pediatric Neurosurgery (T.T.: endowed) and the Charles and Eleanor Clarke Pediatric Neurosurgery Fellowship (D.R.E.: recipient). Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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