Cerebellar ependymoma with overlapping features of clear-cell and tanycytic variants mimicking hemangioblastoma: a case report and literature review.
BACKGROUND
Imaging and histology of clear-cell ependymoma and cerebellum-based hemangioblastoma are similar; distinguishing between them is a diagnostic challenge.


METHODS
A 62-year-old Chinese woman presented with an intermittent headache of 8 years' duration. Computed tomography and magnetic resonance imaging revealed a mass in the cerebellum. Neurological imaging suggested hemangioblastoma (HB). Histologically, the tumor included cellular and paucicellular areas, in which cells were arranged in nests or diffusely distributed; and a highly vascular area, in which tumor cells were arranged in clusters and separated by capillaries. At low magnification, the tumor mimicked cellular HB, but at high magnification, tumor cells showed clear cytoplasm instead of the vacuolated cytoplasm typically observed in HB. Moreover, spindly, bipolar elements resembling tanycytes were observed within the nest structures. Although these features indicated the possibility of ependymoma, neither true ependymal rosettes nor an ependymal-lined profile was observed. The tumor was characterized by prominent vascularity, but glomeruloid formation was absent. We saw pleomorphism in foci of some tumor giant cells, but pathologic mitosis and palisaded necrosis were absent. Most tumor cells were positive for glial fibrillary acidic protein and S100. Epithelial membrane antigen was expressed with a paranuclear dot-like or a ring-like pattern. The Ki-67 index was approximately 2%. Considering the patient's symptom, neurological imaging, and pathological findings, she was diagnosed as cerebellar ependymoma (WHO grade II).


CONCLUSIONS
Here, we report a case of ependymoma with overlapping clear-cell and tanycytic features, and review the literature to evaluate its real incidence. Pathologists should consider this rare diagnosis when confronted with a similar presentation.
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Xiu-Peng
XP
Zhang
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China. liuyanglyon@cmu.edu.cn.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China. liuyanglyon@cmu.edu.cn.
Yang
http://orcid.org/0000-0002-6033-0648
Y
Liu
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Di
D
Zhang
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Qin
Q
Zheng
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Chen
C
Wang
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Liang
L
Wang
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Qing-Chang
QC
Li
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
Xue-Shan
XS
Qiu
Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China.|Institute of Pathology and Pathophysiology, China Medical University, Shenyang, 110001, China.
En-Hua
EH
Wang
D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D001706:Biopsy; D002528:Cerebellar Neoplasms / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D002533:Cerebral Angiography / Q000379:methods; D002872:Chromosome Deletion; D002878:Chromosomes, Human, Pair 1; D002888:Chromosomes, Human, Pair 19; D000072226:Computed Tomography Angiography; D003937:Diagnosis, Differential; D063928:Ependymoglial Cells / Q000737:chemistry / Q000473:pathology*; D004806:Ependymoma / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D005260:Female; D018325:Hemangioblastoma / Q000737:chemistry / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008875:Middle Aged; D060787:Neoplasm Grading; D011237:Predictive Value of Tests
D014408:Biomarkers, Tumor
Case report; Cerebellum; Clear-cell ependymoma; Epithelial membrane antigen; Hemangioblastoma; Tanycytic ependymoma