Solitary Fibrous Tumor in the Liver

Yugawa et al. Surgical Case Reports (2019) 5:68 https://doi.org/10.1186/s40792-019-0625-6

CASEREPORT Open Access Solitary fibrous tumor in the liver: case report and literature review Kyohei Yugawa1,2* , Tomoharu Yoshizumi1, Yohei Mano1, Takeshi Kurihara1, Shohei Yoshiya1, Kazuki Takeishi1, Shinji Itoh1, Noboru Harada1, Toru Ikegami1, Yuji Soejima1, Kenichi Kohashi2, Yoshinao Oda2 and Masaki Mori1

Abstract Background: Solitary fibrous tumors (SFTs) are uncommon mesenchymal neoplasms that present most commonly at intrathoracic sites. SFTs of the liver are rare, with only a few having been reported in the English-language literature. We report a rare case of a hepatic SFT and literature review. Case presentation: A 49-year-old woman underwent surgery for a cranial hemangiopericytoma two decades previously. She currently presented with malaise. Abdominal computed tomography (CT) showed a huge, sharply demarcated mass in the anterior segment of the liver. Tumor marker levels were within the normal range. Following central bisegmentectomy of the liver, histological examination of the specimen revealed that the tumor was composed of spindle and fibroblast-like cells with collagenous stroma. Immunohistochemically, the spindle cells were negative for CD34 but positive for STAT6. The NAB2–STAT6 fusion gene was detected by the reverse transcription polymerase chain reaction. A diagnosis of SFT was thus confirmed histopathologically and genetically. Conclusions: The SFT of the liver is an uncommon finding. Because there are no specific imaging features, it is difficult to diagnose the hepatic SFT preoperatively. We consider that careful surgical resection and postoperative follow-up are necessary for hepatic SFTs. Keywords: Solitary fibrous tumor, Malignant, Radiology and pathology

Background based on histopathological and immunohistochemical fea- Solitary fibrous tumors (SFTs) of the liver are uncom- tures [2, 3]. mon benign tumors. The disease is defined by the World Immunohistochemically, the cluster of differentiation Health Organization (WHO) as a benign tumor originat- 34 (CD34) is a positive marker for mesenchymal tumor ing from submesothelial tissue. Its histological features cells such as are found in SFTs, epithelioid sarcomas, include bland, uniform, fibroblast-like spindle cells and and gastrointestinal stromal tumors (GISTs), exhibiting branching hemangiopericytoma-like vessels [1]. Rarely, it undesirable imperfections in sensitivity and specificity. is found at extra-thoracic sites, including the mediasti- In fact, 5–10% of SFTs are nonreactive to CD34, making num, skin, meninges, orbit, upper respiratory tract, breast, the differential diagnosis of SFTs based on histopath- thyroid, and peritoneum. The hepatic SFT is extremely ology difficult [4]. Recently, several studies revealed out- rare. To our knowledge, including our patient, only 85 standing progress in the diagnosis of SFT based on a cases have been reported in the English-language litera- fusion gene of juxtaposed NGFI-A binding protein 2 ture. In addition, there have been few clinicopathological (NAB2) and signal transducer and activator of transcrip- studies of this rare disease, and the imaging features are tion 6 (STAT6) using both whole-exome sequencing and non-specific, making an imaging diagnosis difficult. Be- integrative sequencing [4–6]. STAT6 has been identified cause of this difficulty, the definitive diagnosis is typically as a highly sensitive, almost completely specific immunohistochemical marker, which distinguishes it from its * Correspondence: [email protected] mimics [7–9]. Although most SFTs exhibit benign be- 1Department of Surgery and Science, Graduate School of Medical Sciences, havior, some have malignant features, including local re- Kyushu University, Fukuoka 812-8582, Japan 2Department of Anatomic Pathology, Graduate School of Medical Sciences, currence [10]. We present a rare case of SFT of the liver Kyushu University, Fukuoka, Japan

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Yugawa et al. Surgical Case Reports (2019) 5:68 Page 2 of 6

and discuss its radiological and pathological diagnostic progressed to persistent, less heterogeneous enhance- features, as well as the possibility of malignancy. ment during the delayed phase (Fig. 1d). Abdominal magnetic response imaging (MRI) showed low intensity on T1-weighted images and heterogeneously Case presentation high or iso intensity on T2-weighted images (Fig. 2a, b). A 49-year-old woman had a history of treatment for a Furthermore, it showed higher intensity than that of nor- cranial meningioma that was diagnosed histologically as mal liver parenchyma on diffusion-weighted imaging a hemangiopericytoma two decades previously. Cur- (DWI) with a high b value of 1000 (Fig. 2d, e). rently, she had no co-morbidities and no alcohol abuse, Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic and she was negative for hepatitis B/C virus. She pre- acid-enhanced magnetic response imaging (EOB-MRI) re- sented with a 1-month history of malaise of unknown vealed a hypointense mass during the hepatobiliary phase cause and abdominal bloating. Analysis of serum tumor (Fig. 2c). [18F]-fluorodeoxyglucose-positron emission tom- markers revealed none that were elevated, including ography (FDG-PET) showed no accumulation of [18F]-FDG α-fetoprotein (3.5 ng/ml), protein induced by vitamin K (Fig. 2f). Radiological evaluation found nothing to suggest absence or antagonist-2 (21 mAU/ml), carbohydrase thepresenceofatumormassanywhereinthebody,includ- antigen 19–9 (19.2 U/ml), and carcinoembryonic antigen ing no cranial or spinal lesions. Gastroscopy and colonos- (0.8 ng/ml). Other parameters were within their normal copy findings were normal. According to radiological ranges. examination, the preoperative diagnosis was a malignant The patient underwent abdominal computed tomog- tumor, such as scirrhous hepatocellular carcinoma (HCC), raphy (CT), which revealed a large mass involving al- sarcomatous HCC, GIST, or hemangiosarcoma. The patient most the entire right lobe of the liver. It measured 14 cm then underwent central bisegmentectomy of the liver. in maximum diameter and was compressing the inferior Macroscopically, the maximum diameter of the tumor vena cava (Fig. 1a). Contrast-enhanced CT showed was 13.3 cm, and the tumor itself was firm and marked heterogeneous enhancement in the periphery of yellowish-white with an intact capsule. Hemorrhagic the mass during the arterial phase (Fig. 1b), with the en- areas and horizontal intertwined fiber bundles were ob- hancement becoming centripetal and more pronounced served on the cut surface of the tumor (Fig. 3a). Micro- in round unenhanced areas related to necrotic or cystic scopically, the tumorous tissue showed proliferation of changes during the portal phase (Fig. 1c). It finally oval to short spindle-shaped cells arranged in no

Fig. 1 Contrast-enhanced abdominal computed tomography (CT). Plain CT shows a well-defined low-density mass occupying the right lobe (14.0 cm diameter) (a). Contrast-enhanced CT shows heterogeneous enhancement in the peripheral mass during the arterial phase (b). Enhancement is then centripetal and more pronounced during the portal phase (c) and finally progresses to persistent, less heterogeneous enhancement during the delayed phase (d) Yugawa et al. Surgical Case Reports (2019) 5:68 Page 3 of 6

Fig. 2 Magnetic resonance imaging (MRI) and [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET). Abdominal MRI shows low intensity on a T1-weighted image (a) and heterogeneously high or iso intensity on a T2-weighted image (b). Gadolinium-ethoxybenzyl- diethylenetriamine pentaacetic acid-enhanced MRI reveals a hypointense mass during the hepatobiliary phase (c). Diffusion-weighted imaging shows higher intensity than for normal liver parenchyma (d) with a high b value of 1000 (e). FDG-PET shows no accumulation of [18F]-FDG (f)

a b

cde f

Fig. 3 Macroscopic and microscopic findings of SFT. Macroscopically, the tumor mass was firm and yellowish-white with an intact capsule (13.3 cm maximum diameter) (a). Microscopically, the tumorous tissue showed a proliferation of oval to short spindle-shaped cells arranged in a “pattern-less pattern” (H&E × 400) (b). Immunohistochemically, the tumor cells were negative for CD34 (× 400; c), but positive for STAT6 (nuclei, × 400) (d) and vimentin (× 400) (e). Ki67 labeling index was < 5% (× 400) (f) Yugawa et al. Surgical Case Reports (2019) 5:68 Page 4 of 6

particular pattern, accompanied by focal Following surgery, the patient recovered uneventfully. At fibro-collagenous or myxoid stroma and a few heman- present, 12 months postoperatively, she remains well with giopericytomatous branching vessels. Foci of no evidence of tumor recurrence. hemorrhage and necrosis were observed. Mitotic figures were present, although rare, highlighted by hematoxylin Discussion and eosin (HE) staining [< 1/20 high-power fields First described in 1931 [11], SFT has since appeared in (HPFs)] (Fig. 3b). There was no vascular or parenchymal the form of hemangiopericytoma, giant cell angiofi- invasion. broma, fat-forming variant, lipomatous hemangiopericy- Immunohistochemically, the tumor cells were negative toma, and, rarely, as a mesenchymal neoplasm that for CD34 (Fig. 3c) but positive for STAT6 (Fig. 3d) and commonly originates from pleura. In the 2013 WHO vimentin (Fig. 3e). No markers of HCC (hepatocytes, classification of tumors of soft tissue and bone, extra- glypican-3) or GIST (S100 protein, cKIT, DOG1) were pleural SFT was considered a fibroblastic/myofibroblas- conspicuous in the specimen (not shown in Fig. 3). The tic neoplasm with intermediate, rarely metastasizing Ki67 labeling index was < 5% (Fig. 3f). NAB2–STAT6 fu- biological behavior [1]. Subsequently, in the updated sion gene was detected by reverse transcription-polymer- WHO classification of the digestive system, SFT is con- ase chain reaction (RT-PCR) and direct sequencing. Gel sidered a benign tumor with the potential for malignant electrophoresis of PCR products identified various NAB2– transformation [12]. Because the hepatic SFT is ex- STAT6 fusions with heterogeneous exon compositions in tremely rare, whether the SFT should be classified as a the tumor using seven primer pairs (Fig. 4a). Direct se- benign or malignant tumor remains controversial re- quencing showed the junction breakpoint in a stretch of garding this tumor originating from the liver. NAB2 intronic sequences between the 3′-end of NAB2 Only 85 patients with SFTs of the liver, including ours, exon 6 and the 5′-end of STAT6 exon 16 (Fig. 4b). Thus, have been reported in the English-language literature. SFT of the liver was diagnosed definitively based on these According to the review by Chen et al. [13], the average histological and genetic results. The surrounding liver age of patients with this affliction is 57.1 (range 16–87) showed mild inflammation in the normal portal area. years. It appears to occur more frequently in women

a (bp)

300 - 200 - 100 - NAB2ex2-STAT6ex6 (106bp) 100bp Ladder PGK(189bp) (internal cont.) PGKp(100bp) (internal cont.) NAB2ex4-STAT6ex2 (122bp) NAB2ex6-STAT6ex16 (152bp) NAB2ex6-STAT6ex17 (154bp) NAB2ex6-STAT6ex18 (152bp) NAB2ex2-STAT6ex2 (128bp) 100bp Ladder NAB2ex4-STAT6ex3 (103bp)

b NAB2 exon6 STAT6 exon16

Fig. 4 NAB2–STAT6 fusion gene in the SFT identified by RT-PCR and sequencing. Gel electrophoresis of PCR products reveals the various NAB2–STAT6 fusion genes with heterogeneous exon compositions in the tumor, which were identified using seven primer pairs (a). Direct sequencing shows the junction breakpoint in a stretch of NAB2 intronic sequence between the 3′-end of the NAB2 exon 6 and the 5′- end of the STAT6 exon 16 (b) Yugawa et al. Surgical Case Reports (2019) 5:68 Page 5 of 6

than in men (1.4:1.0), and the histological incidence of liver tumors. However, CD34 staining is imprecise in this malignant features is 19.0% (16/84 patients). The clinical case because 5–10% of typical SFTs are nonreactive to presentation of this disease is generally non-specific. CD34 [1]. To make up for this imprecision, the NAB2– Extrapleural SFTs present as relatively slow-growing STAT6 fusion gene has recently been identified as the gen- masses that are often asymptomatic. When symptoms do etic hallmark of SFT. This aberration drives the nuclear occur, they are caused by the pressure the mass exerts on relocation of STAT6 [6]. Immunohistochemical detection adjacent structures [14]. Similarly, our patient complained of STAT6 nuclear expression and the NAB2–STAT6 fu- of steadily increasing abdominal bloating at presentation, sion gene identified by RT-PCR assay offers a strong sur- which proved to be due to the huge tumor compressing rogate diagnostic technique for distinguishing SFTs from other organs. In previous reports, hepatic SFTs were histological mimics. Our patient, in fact, was immunohis- found incidentally during routine examinations. tochemically negative for CD34, which made the definitive Among radiological studies, ultrasonography often re- diagnosis difficult. However, the spindle cells were immu- veals a heterogeneous mass that may be either hypoe- nohistochemically positive for STAT6, and the NAB2– chogenic or hyperechogenic (or both) with or without STAT6 fusion gene was detected by RT-PCR and direct se- calcification. Contrast-enhanced CT shows early arterial quencing, thereby allowing a definitive SFT diagnosis. enhancement with delayed venous washout. MRI of our Chen et al. [13] previously reported that 16 of 84 SFTs patient showed that the tumor mass was heterogeneous were malignant, which was similar to the intrapleural with slight hyperintensity on T2-weighted images and SFT recurrence rate of 20–67% among malignant tu- slight hypointensity on T1-weighted images. Findings on mors. These malignant cases were diagnosed by histo- MRI are similar to those seen on CT scans. DWI re- logical examination, which showed a high incidence of vealed greater signal intensity than that of normal liver mitotic changes (> 4/10 HPF) and local recurrence or [15]. These findings often mimic those of high-grade distant metastasis in 17.9%. Furthermore, 26.7% of pa- HCCs (including scirrhous and sarcomatous HCC) or tients with these malignant SFTs had a local recurrence leiomyomas. Our radiological results were consistent within 9 months to 6 years, and 53% had distant metas- with these patterns. tasis within 1 month to 6 years. England et al. [18] estab- In our case, a percutaneous biopsy was not performed lished the criteria for malignant SFT: mitotic changes (> to obtain a tissue diagnosis. Although a fine-needle bi- 4/10 HPFs), tumor necrosis and hemorrhage, nuclear opsy can distinguish the SFT from malignant tumors pleomorphism, and metastasis were the major criteria, such as HCC or sarcoma, the procedure could lead to and large tumor size (> 10 cm) and cellular atypia were rupture or seeding of malignant cells. Some reports sug- the minor criteria. Wilky et al. [19] classified the SFTs gested that, although liver biopsy could be performed into “benign” with no England’s criteria, “borderline” safely, the biopsy of the SFT was misdiagnosed as HCC with 1 or more England’s criteria but final classification or metastasis from adenocarcinoma of the pancreas or a as benign, and “malignant.” This report described that gastrointestinal tract lesion [16, 17]. In our patient, the “borderline” SFTs with any of England’s criteria had been possibility of a malignant tumor could not be ruled out related to high risk of recurrence. Our patient described preoperatively because we decided to resect this huge herein met two of the six criteria (necrosis/hemorrhage tumor without a definitive diagnosis due to the patient’s and tumor size), suggesting a possibility of malignancy. symptoms and the risk of hemorrhage. SFTs of the head, neck, and intracranial meninges are A definitive diagnosis of SFT of the liver requires histo- also rare and display benign behavior without metastasis pathological and immunohistochemical studies. Micro- [20]. We found no descriptions in the English-language scopically, the tumor is composed of ovoid spindle-shaped literature that resembled that of our patient, who pre- cells with its characteristic architecture in a storiform pat- sented with suspected localized liver metastasis from a tern or a haphazard, “patternless pattern.” These cells are head SFT. Du et al. [21], however, reported a rare case separated from thick bands of keloid-like collagen bundles of non-malignant SFT that appeared 5 years after initial and display branching of staghorn vessels in a liver resection. The tumor’s appearance had no marked hemangiopericytoma-like pattern. Myxoid changes are variances from other non-malignant SFTs. also commonly observed. Mitoses and necrotic changes— To clarify whether this second tumor was a recurrence characteristically suggesting malignancy—are rare for this from a cranial SFT in our patient, we attempted to tumor [13]. Features identified by WHO as being associ- examine specimens from her previous, cranial SFT. Un- ated with malignancy include hypercellularity, cytological fortunately, no tissue was available because the mainten- atypia, tumor necrosis, infiltrative margins, and high mi- ance term of the specimen had reached its limit, and it totic activity (≥ 4/10 HPF) [1]. had been discarded. Assessment of the radiological find- Immunohistochemically, the staining of CD34, vimen- ings, however, showed that there had been no abnormal- tin, and Bcl-2 is useful for distinguishing SFTs from other ity in other organs, and no important mitotic changes or Yugawa et al. Surgical Case Reports (2019) 5:68 Page 6 of 6

low levels of the Ki67 labeling index. Thus, it was more classification of tumours of soft tissue and bone. fourth ed. Lyon: IARC; likely that our patient currently had a primary tumor in 2013. p. 74–8. 2. Fama F, Le Bouc Y, Barrande G, Villeneuve A, Berry MG, Pidoto RR, Saint the liver rather than a recurrence from her original cra- Marc O. Solitary fibrous tumour of the liver with IGF-II-related nial SFT. Nevertheless, we are committed to performing hypoglycaemia. A case report. Langenbeck's Arch Surg. 2008;393:611–6. carefully follow-up every 3 months in the first 2 years, 3. Novais P, Robles-Medranda C, Pannain VL, Barbosa D, Biccas B, Fgaca H. Solitary fibrous liver tumor: is surgical approach the best option? J twice each year up to 5 years after surgery, and then Gastrointestin Liver Dis. 2010;19:81–4. once a year after the fifth year. The best method for 4. Chuang IC, Liao KC, Huang HY, Kao YC, Li CF, Huang SC, Tsai JW, Chen KC, follow-up is not well established, but whole-body CT is Lan J, Lin PC. NAB2-STAT6 gene fusion and STAT6 immunoexpression in extrathoracic solitary fibrous tumors: the association between fusion variants suggested in our patient. and locations. Pathol Int. 2016;66:288–96. 5. Robinson DR, Wu YM, Kalyana-Sundaram S, Cao X, Lonigro RJ, Sung YS, Conclusions Chen CL, Zhang L, Wang R, Su F, Iyer MK, Roychowdhury S, Siddiqui J, Pienta KJ, Kunju LP, Talpaz M, Mosquera JM, Singer S, Schuetze SM, According to previous reports, SFT of the liver is an ex- Antonescu CR, Chinnaiyan AM. Identification of recurrent NAB2-STAT6 gene tremely rare and benign tumor. Because of the few clinico- fusions in solitary fibrous tumor by integrative sequencing. Nat Genet. 2013; pathological specific features, it is difficult to diagnose this 45:180–5. 6. Chmielecki J, Crago AM, Rosenberg M, O'Connor R, Walker SR, Ambrogio L, tumor. We performed the resection of the tumor and de- Auclair D, McKenna A, Heinrich MC, Frank DA, Meyerson M. Whole-exome finitively diagnosed SFT of the liver histopathologically and sequencing identifies a recurrent NAB2-STAT6 fusion in solitary fibrous genetically. We consider that careful surgical resection and tumors. Nat Genet. 2013;45:131–2. 7. Yoshida A, Tsuta K, Ohno M, Yoshida M, Narita Y, Asamura H, Kushima R. postoperative follow-up are necessary for hepatic SFTs. STAT6 immunohistochemistry is helpful in the diagnosis of solitary fibrous tumors. Am J Surg Pathol. 2014;38:552–9. Abbreviations 8. Barthelmess S, Geddert H, Boltze C, Moskalev EA, Bieg M, Sirbu H, Brors B, CD34: Cluster of differentiation 34; CT: Computed tomography; Wiemann S, Hartmann A, Agaimy A, Haller F. Solitary fibrous tumors/ DWI: Diffusion-weighted imaging; EOB-MRI: Gadolinium-ethoxybenzyl- hemangiopericytomas with different variants of the NAB2-STAT6 gene diethylenetriamine pentaacetic acid-enhanced magnetic response imaging; fusion are characterized by specific histomorphology and distinct 18 FDG-PET: [ F]-fluorodeoxyglucose positron emission tomography; clinicopathological features. Am J Pathol. 2014;184:1209–18. GIST: Gastrointestinal stromal tumor; HCC: Hepatocellular carcinoma; 9. Cheah AL, Billings SD, Goldblum JR, Carver P, Tanas MZ, Rubin BP. STAT6 HE: Hematoxylin and eosin; MRI: Magnetic response imaging; NAB2: NGFI-A rabbit monoclonal antibody is a robust diagnostic tool for the distinction of binding protein 2; RT-PCR: Reverse transcription polymerase chain reaction; solitary fibrous tumour from its mimics. Pathology. 2014;46:389–95. SFT: Solitary fibrous tumor; STAT6: Signal transducer and activator of 10. Sun K, Lu JJ, Teng XD, Ying LX, Wei JF. Solitary fibrous tumor of the liver: a transcription 6; WHO: World Health Organization case report. World J Surg Oncol. 2011;9:37. 11. Klemperer P, Rabin CB. Primary neoplasms of the pleura. A report of five Acknowledgements cases. Am J Ind Med. 1992;22(1):1–31. We thank Nancy Schatken, BS, MT (ASCP), from Edanz Group (www. 12. Miettine M, Fletcher CDM, Kindblom L, Zimmermann A, Tsui WMS. edanzediting.com/ac), for editing a draft of this manuscript. Mesenchymal tumoours of the liver. In: Bosman FT, Carnerio F, Hruban RH, Theise ND, editors. WHO classification of tumours of the digestive system. Funding fourth ed. Geneva: Lyon, IARC Press; 2010. p. 241–50. Not applicable. 13. Chen N, Slater K. Solitary fibrous tumour of the liver—report on metastasis and local recurrence of a malignant case and review of literature. World J Availability of data and materials Surg Oncol. 2017;15:27. Not applicable. 14. Ronchi A, Cozzolino I, Zito Marino F, Accardo M, Montella M, Panarese I, Roccuzzo G, Toni G, Franco R, De Chiara A. Extrapleural solitary fibrous Authors’ contributions tumor: a distinct entity from pleural solitary fibrous tumor. An update on KY acquired the data and drafted the manuscript. KY, YM, and TY performed clinical, molecular and diagnostic features. Ann Diagn Pathol. 2018;34:142– the surgery. All other authors attended the patient postoperatively. All 50. authors read and approved the final manuscript. 15. Soussan M, Felden A, Cyrta J, Morere JF, Douard R, Wind P. Case198: solitary fibrous tumor of liver. Radiology. 2013;269(1):304–8. Ethics approval and consent to participate 16. Korkolis DP, Apostolaki K, Aggeli C, Plataniotis G, Gontikakis E, Volanaki D, No applicable. Sebastiadou M, Dimitroulopoulos D, Xinopoulos D, Zografos GN, Vassilopoulos PP. Solitary fibrous tumor of the liver expressing CD34 and Consent for publication vimentin: a case report. World J Gastroenterol. 2008;14(40):6261–4. Oral informed consent was obtained from the patient for the publication of 17. Fuksbrumer MS, Klimstra D, PanicekDM. Solitary fibrous tumor of the liver: this case report and accompanying images. imaging findings. AJR Am J Roentgenol. 2000;175:1683–7. 18. England DM, Hochholzer L, McCarthy MJ. Localized benign and malignant Competing interests fibrous tumors of the pleura: a chlinicopathological review of 223 cases. Am The authors declare that they have no competing interests. J Surg Pathol. 1989;13:640–58. 19. Wilky BA, Montgomery EA, Guzzetta AA, Ahuja N, Meyer CF. Extrathoracic ’ location and borderline histology are associated with recurrence of solitary Publisher sNote fibrous tumors after surgical resection. Ann Surg Oncol. 2013;20:4080–9. Springer Nature remains neutral with regard to jurisdictional claims in 20. Carneiro SS, Sheithauer BW, Nascimento AG, Hirose T, Davis DH. Solitary published maps and institutional affiliations. fibrous tumor of the meninges: a lesion distinct from fibrous meningioma. A clinicopathologic and immunohistochemical study. Am J Clin Pathol. Received: 7 March 2019 Accepted: 5 April 2019 1996;106(2):217–24. 21. Du EHY, Walshe TM, Buckley AR. Recurring rare liver tumor presenting with hypoglycemia. Gastroenterology. 2015;148:e11–3. References 1. Fletcher CD, Bridge JA, Lee JC. Extrapleural solitary fibrous tumor. In: Fletcher CD, Bridge JA, Hogendoorn PCW, Mertens F, editors. WHO