대 한 방 사 선 의 학 회 지 1992 ; 28 (1) : 14 암~155 Journal of Korean Radiological Society. January. 1992

Primitive Neuroectodermal Tumors in the Posterior Fossa: Excluding Medulloblastoma Based on Pathology

Kyung Jin Suh, M.D., Tae Hun Kirn, M.D., Yong Joo Kirn, M.D., Duk Sik Kang, M.D. Sun Young Kirn, M.D. *, Youn Kyung Shon, M.D. * *

Department of Diagnostic Radiology. ColJege o[ Medicine. Kyungpook National UniverSity

- Abstract-

Four children. with histopathologicaJly confirmed posterior fossa primitive neuroectodermal tumors. were ex­ amined by plain radiography. computed tomography (CT) and cerebral angiography. The homogeneously weJl enhanc­ ed solid mass in the midline of the posterior fossa and hydrocephalus of various degree were seen on a Jl CT scans. One case had calcifications and another case had low density areas in the tumor mass. Three cerebral angiograms showed vascular displacement without tumor vascularities. Unfortunately. these CT and angiography findings are not specific for primitive neuroectodermal tumors. as similar findings are seen in meduJloblastoma. ependymoma and other tumors. Therefore. we think that the primitive neuroectodermal tumors should be included in the differential diagnosis when a weJl enhanced solid mass in the midline posterior fossa is seen on CT scan in children.

Index Words: Brain. neoplasm 10.36 CerebeJlar neoplasm 153.36 Primitive neuroectodermal tumor 10.369

retinoblastoma and olfactory neuroblastoma. It INTRODUCTION should be noted they included medulloblastoma in the posterior fossa as primitive neuroectodermal Primitive neuroectodermal tumors were first tumors. Chatty(3) reported these terms have been us­ described by Hart and Earle(l) in 1973. They describ­ ed to describe various tumors. which most often arise ed a group of supratentorial tumors that closely in the cerebellum of children and have traditionally resembled microscopically germinal or matrix cells been called meduUoblastoma. Rubinstein(4). of the primitive neural tube. There are a lot of opi­ however. reported this indiscriminate applicatioin of nions about the primitive neuroectodermal tumor a simplistic concept that would include all the so­

classification. Becker and Hinton(2) categorized and called “ primitive neuroectoderma1 tumors" into a described the pathology of primitive neuroectodermal single neuroepithelial tumor entity is unlikely to tumors. Previous articles classified primitive neuroec­ bring further understanding to the problem. Russel todermal tumors. including medulloblastoma. et al(5) said primitive neuroectodermal tumors and medulloepithelioma. neuroblastomas. polar spong­ medulloblastomas differ histogenetica1ly. We recent1y ioblastoma. pinealoblastoma. ependymoblastoma. reviewed posterior fossa primitive neuroectodermal

*영 남대학교 의과대 학 진 단방사선과학교실 *Department o[ Diagnostic Radio1ogy. College o[ Medicine. Youngnam University

**경북대학교 의 과 대학 해 부병리학교실 **Department o[ Anatomic Pathology. College o[ Medicine. Kyungpook National University 이 논 문은 1991 년 2 월 23 일 접 수하여 1991 년 10 월 11 일에 채택되었음 Received February 23. Accepted October 11. 1991 - 149- Journal of Korean Radiological Society 1992 ; 28( 1) : 149~ 155 tumors and accumulated 4 cases that fall into a Table 1. Profile ofPatients with Primitive Neuroectoder- category based on pathologic diagnosis. mal Tumors Our goal was to be able to make a resonable Case Age/Sex CT Angiographic Others diagnosis and differnetial diagnosis with radiologic No. Findings Findings studies. so that the clinician can know the tumor 121M Hydrocephalus Vessel displace behavior and it’ s possible rapid course and hence. Mass No tumor vessel proper and more aggressive therapy may be planned Midline Calcification SUBJECTS AND METHODS Well enhance 2 141F Hydrocephalus From December 1988 to September 1989. three Mass cases of primitive neuroectodermal tumors in the Midline Low density portion posterior fossa were diagnosed at Kyungpool‘ Na­ Well enhance tional University Hospital and one case at Youngnam University Hospital. All patients underwent opera­ 3 141M Hydrocephalus Negative study Spinal MRI Mass Metastasis tion. and afterwards histologic proof was obtained. Midline There were two males and two females between 12 Hyperdense portion and 15 years of age. Images were taken from a ll pa Well enhance tients using plain radiography and CT scans with and Meningeal enhancement without contrast enhancement. We performed 4 121F Hydrocephalus Vessel displace cerebral angiography on three pa디 ents. Suspecting Mass No tumor vessel spinal metastasis in one patients. a spinal MR imag­ Paramedian ing was obtained (Table 1). Clinically. all pa tients Well enhance showed signs of increased intracranial pressure. evi­ dent by headache and vomiting. A 12 year old boy was a dmitted with a persistent vomiting of 10 day's duration. The skull series were CASE REPORTS n egative. Cranial CT scan revealed mode rate Case 1 hydrocephalus. In the midline of the posterior fossa.

a b c Fig. 1. Case 1. a. Nonenhanced CT scan shows a slightly hyperdense midline mass with hydrocephalus and intratumoral calcification b. Contrast enhanced CT scan shows marked tumoral enhancement with relatively little adjacent edema c. Lateral projection of vertebral arteriogram shows vascular displacement without tumor neovascularity

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distributed chromatin. However, the cells had scan­ ty cytoplasm and no nucleoli. The boundary of the cytoplasm was not distinct. A small number of the multinucleated giant cells were observed. The tumor cells were arranged in a compact sheet without rosette or psedorosette formation. There were a lot of mitotic figures. Marked vascular proliferation and prominant collagen deposite were encountered in the stromal tissue. Immunohistochemical study for glial fibrillary acidic protein (GFAP) and neurofillament (NF) protein revealed negative findings (Fig. ld). ld Fig. l.d. Photomicroscopic feature shows small round Case 2 tumor cells without organoid pattern. Several giant cells are scattered. (H&E x 100) This patient was a 14 year old girl who had h eadaches and vomitings for 10 months. Bilateral there was a mass measured as 4.5 x 4cm in size. It papilledema with optic atrophy and nystagmus were had nodualr calcifiations and was well enhanced. No presen t. Three different times CSF cytology studies peritumoral edema was evident. Cerebral revealed a Clas3 1 result. Plain skull showed diastatic angiography showed vessel displacement without suture lines and dorsum sella widening. A cranial CT tumor vascularity (Fig. 1). After total removeal ofthe scan revealed severe hydrocephalus and a midline tumor the patient developed stress ulcer bleeding, mass in the posterior fossa. The mass, 4.8 x 3.6cm in hence we performed gastroduodenal artery emboliza­ size, had no calcification. After a contrast injection , tion with Gelfoam and surgical intervention follow- the mass became wel1 enhanced and showed some ed. Brain radiotherapy was also done. low density portions which were be tumor necrosis. Pathologic examination proved the the tumor was The peritumoral edema was scanty (Fig. 2). After total of a primitive neuroectodermal origin. The tumor removal of the tumor, radiation therapy was given cells showed small round nucleus and relatively even

a b c Fig 2. Case 2. a and b. Nonenhanced and enhanced CT scans show a hyperdense midline mass with low density portions. c. A higher cut shows moderate hydrocephalus.

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before admission. a brain CT scan showed subarachnoid enhancement. and subdural effusion but no hydrocephalus. After being admitted because of aggravation of his symptoms. a cranial CT scan revealed mild hydrocephalus. meningeal enhance­ ment and a mass in the midline at the posterior fossa. The well enhanced mass. 1.8x 2cm in size. showed questionable areas of calcification. and little peritumoral edema. Cerebral angiogram revealed no tumor vascularities or displacement. Since we

suspected spinal metastasis. spin머 MR imaging was done. The MR imaging revealed high signal intensi. ty on T2 WI in the spinal cord at the level of the 6th and 7th thoracic vertebrae. Both posterior fossa and spinal cord lesions proved to be primitive neuroec. todermal tumors (Fig. 3). The tumor cells showed two different kinds of cell type. One was undifferentated neuronal cells with small round nuc1ei. The other was spindle cells with long cytoplasmic process. Undif. ferentiated neuronal cells aggregated without rosette. At the interstitial portion. deposition of collagen fibers and ground substance was noted. Spindle ce\ls reveal­ 2d Fig. 2.d. Uniform small round cells are noted. Fine ed cellular atypia with occasional mitosis. Both fibrillary are seen in the background with vascular pro. cerebral and spinal tumors revealed the same liferations. (H&E x 100) features. The immunohistochemical study for GAP Case 3 revealed weak positive findings and the study for NF This patient was a 14-year.old boy a ff1 icted with revealed posivie features in the cytopolasms of tumor three days of headaches and vomiting. One month cells. Most of the positive features of NF were noted

a b C Fig 3. Case 3. a. Nonenhanced CT scan shows a hyperdense small midline mass with hydrocephalus. b. Contrast enhanced CT scan shows tumoral and meningeal enhancement. c. Lateral projection of vertebral arteriogram shows no abnormality

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DISCUSSION

Primitive neuroectoderma is a term that has been used to describe the tota1 substance of the central ner­ vous system excluding the mesenchymal elements. which are bloood vessels and microglia(l). Primitive neuroectodermal tumors are large masses most com­ monly of the fronatal lobes that show ca1cifications and cystic components(6.7). The tumors are malig­ nant lesions with a high rate of recurrence after 3d therapy and frequent subarachnoid metastases. Like Fig. 3.d. Primitive tumor cells are aggregated. Fibrous stromas are noted. (H&E x 100) other central nervous system neoplasm found in childhood. these tumors of the posterior fossa are in the cytoplasm of spindle shaped tumor cells (Fig. biologically poorly understood. Even the classifica­ 3d.4b). tions of the primitive neuroectodermal tumors­ medulloblastoma are controverisa1 . Rorke( 11) propos­ Case 4 ed a c1assification wherein all embryonic small cell A 12 year old girl was admitted to Youngnam neuroepithelial tumors ofthe central nervous system University Hospital. for evaluation of diziness. would be regared as primitive neuroectodermal weakness. vertigo and headches. She had an acute tumors and then they were subdivided on their basis posterior right lateral headache and menta1 changes. oflight microscopic evidence for differentiation along A cranial CT scan presented a 4.5 x 2.3Cm sized the various cell lines (such as medulloblastoma. paramedian well enhanced mass in the posterior pinea1oblastoma). Becker et 외 (2) in 1983 reported the fossa with obstructive hydrocepha1 us. On the cerebra1 medulloblastoma can be considered a primitive angiogam . the mass displaced the vessels without neuroectoderrnal tumor of the posterior fossa. Russel tumor vascularitis. and Rubinstein(5) strongly disagree with this

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- 153- Journal of Korean Radiological Society 1992 ; 28( 1) : 149~ 155 classification. They argue for retaining the term case in our study revealed thoracic spina\ cord

“ medulloblastoma" for primitive neuroectodermal metastasis tumors in the posterior fossa. Their argument being Based on radiologic findings differential diagnoses that the histogenesis of this portion of the central considered in our cases included medulloblastoma neuraxis (specifically the cerebellum) is unique and and ependymoma. During our study. pre-and the clinical course for patients who have tumors in postcontrast CT scans were good available imaging this location are better delineated than that from technique for evaluating these lesions. Angiography. primitive neuroectodermal tumors arising elsewhere although not essential. was primarily used as an an­ in the central nervous systems. Recent1 y some cillary technique for studying tumor vascularity and authors have published radiologic findings of cerebral fe eding vessels. In our cases MR imaging showed primary neuroblastomas diffemtiating from primitive spinal metastasis well n euroectodermal tumors( 12). Our cases of primitive Although we experienced a limited number of neuroectoderaml tumors showed cytologic case‘ our investigations suggest that. CT and characteristics such as anisocytosis. giant cell forma angiographic findings of primitive neuroectodermal tion and spindle cells. The arrangement of tumor cells tumors in the posterior fossa were not specific. in our cases revealed no rosette or pseudorosette for­ Therefore there should be careful considering in the mation that is the most characteristic feature in differenetial diagnosis of midline tumors of the medulloblastomas. The stroma of the these cases posterior fossa. Our experience supports that showed marked collagen deposite that is not noted histopathological confirmation should be required for in pure brain cell tumors such as medulloblastomas definitediagnosis of primitive neuroectodermal or other astrocytomas. tumors. The age for primitive neuroectodermal tumor onset on the cerebrum occurs in patients from birth REFERENCES till 24 years of age(9). The mean age of our patients l ‘ Hart MN . Earle KM. Primitive neuroectodermaL were 13 years. The symptoms and signs were usual­ tumors of the brain in children. Cancer ly nonspecific. consistent with a posterior fossa mass 1974:32:890-897 and increased intracranial pressure. such as 2. Becker LE. Hinton O. Primitive neuroectodermal headaches. nausea. and vomiting( 10). One case of the tumors ofthe central nervous system. Hum Pathol plain radiography showed increased intracranial 1983:14‘ 535-550 pressure signs. The masses were situated at the 3. Chatty EM. Earle KM. Medulloblastoma. A report of midline or the paramedian along the cerebellar ver­ 201 cases with emphasis on the histologic variants mis like where the medulJ oblastoma would be to survival. Cancer 197 1;81 :977 -983 located. The CT scan showed some of the well 4. Rubinstein LJ. Embryonal central neuroepithelial enhanced masses had calcification or low density por­ tumors and their differentiating potential. A tions. AIJ cases showed hydrocephalus. Cerebral cytogenetic view of a complex neuro-oncological pro­ angiography showed non-specific findings such as blem. J Neurosurg 1985:62(6):795-805 vascular displacements without tumor vascularities. 5. Russel OS. Rubinstein LJ. Pathology of tumors of the nervous system. 5th ed. Baltimore: Williams and Unfortunately we couldn’ t obtain specific radiologic Wilkins. 1989:251-279 findings of primitive neuroectodermal tumors. 6. Ganti SR. Silver AJ. Oiefenbach P. Hilal SK. Mawad Gcorge et al(l3) reported 42% of posterior fossa ME , Sane P. Computed tomography of primitive primitive neuroectodermal tumors were identified as neuroectodermal tumors. AJNR 1983;4:819-821 m etastasis and all were noted to have deposits in the 7. Altman N, F'itz CR. Chung S. Hawawood-Nash D, thoracic region. All children with metastases were Cotter C. Armstrong C. Radiologic characteristics less than 3 years old and had differentiated primitive of primitive neuroectodermal tumors in Children. n euroectodermal tumors. Using MR imaging. one AJNR 1985‘ 6:15-18

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8 . Kosnik EJ. Boesel CP. Bay J ‘ Sayers MP. Primitive J Ne urop a th 미 Exp Neurol 1983 ‘ 42:1-15 n euroectoderma l tumors of the central nervous 12. Davis PC. Wichman RD. Ta kei Y. Hoffma n JC. system in children. J Neurosurg 1978:48:741-746 Prima ry cerebral neuroblastoma : CT and MR fin-

9. Duffner PK‘ Cohen ME. Heffner RR. Freeman AI. dings in 12 cases. AJR 1990‘ 154:831-836 Primitive neuroectodermal tumors ofchildhood. J 13. George RE. Lauren t JP. McCluggage CW. Cheek Neurosurg 1981 :55:376-381 WR. Spinal metastasis in primitive neuroectodermal 10. Gusnard DA. Cerebellar neoplasms in children. tumors of the posterior fossa: Eva lua tion with CT

S emin Roentgenol 1990‘ 25[3):263-278 myelography and corelation with pa tient age and 11. Rorke LB. The cerbellar m edulloblastoma and its tumor difference. Pediatr Neurosci 1985-1986: relationship to primitive ne uroectodermal tumors. 12[3): 157 -160

<국문 요약> 후두개강의 원시성 신경외배엽성종앙

경북대학교 의과대학 진단방사선과학교실， 영남의대 방사선과 * 경북의대 해부병리과 **

서경진 • 김태헌 • 김용주 • 강덕식 • 김선용* • 손윤경**

원 시 성 신 경외매엽성 종양은 소아의 대뇌에 호발하는 예후가 극히 나쁜 악성종양이다. 저자들은 최근 l0 7H 월간 수술후 병리학적으로 확진된 4 례의 소아의 후두개강내에 발생한 원시성 신경외배엽성 종양의 방사선학적 소 견을 분석해 본 결과 뇌 전산화단층촬영상 전례에서 후두강 중앙 부위의 제 4뇌실의 뒷쪽에 종양이 위치하였으며 다양한 정 도 의 수두증 및 균 질의 심한 조영증강을 보였다. 종괴내에 석회화와 낭성 혹은 괴사성부위로 생각되는 저음영부위를 보인 예가 각각 1 례씩 있었으며 척수전이를 보인 1 례에서는 뇌 전산화단층촬영상 뇌막의 조영증강을 보 였 다. 3 례에서 시행한 뇌 혈관촬영에서 종양혈관은 없었으며 종괴에 의한 혈관 전위의 소견만 관찰되었다. 적은 예이지만 방사선학적으로 수아 세포종이나 상의 세포종등과 감별할만한 특이한 소견은 없었으며 소아의 후두개강내에 발생한 조 영 증강이 잘되는 중앙부위의 종양의 방사 선학적 감별진단시 원시성 신경외배엽성 종양이 포항되어야 할 것으로 생각된다.

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