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3 June 2011 – Case of the Week #208
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Thanks to Javier Ortiz, Pablo Sousa, Margarita López Candocia, Marta Rodríguez, and Agustín Bullón (Hospital Universitario de Salamanca and Hospital Virgen Vega de Salamanca, Spain), for contributing this case and the discussion. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.
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Case of the Week #208
A 66 year old man was admitted for the subacute onset of mild disequilibrium and vertigo. He had a previous history of peptic ulcer and smoking. CT scan and MRI revealed a well-defined solid mass lesion in the fourth ventricle extending into the foramen magnum. Clinical testing for metastatic disease was negative.
H&E images and GFAP (right)
What is your diagnosis?
Giant cell ependymoma
Histological examination showed a neoplasm with unipolar processes extending from elongated tumor cells toward blood vessels in perivascular rosettes, typical of ependymoma. Multiple giant tumor cells are also present, usually with well defined borders, eosinophilic cytoplasm and bizarre, hyperchromatic nuclei. No areas of vascular proliferation, glomeruli-like structures, or necrosis were seen. The tumor cells had low proliferative activity by Ki-67 staining (<1%). Most tumor cells (classic ependymoma and giant cells) were strongly immunoreactive for GFAP and negative for epithelial (AE1/AE3 and CAM5.2), melanocytic (HMB-45 and Melan A) and histiocytic markers (CD68). There was focal perinculear staining for EMA. In contrast to previous reports (7), inmunostaining for CD99 was not observed in this case. The reticulin stain showed minimal reticular architecture, in agreement with the soft appearance of the neoplasm.
This uncommon ependymoma variant can occur throughout the neuraxis, with some preference for filum terminale and spinal cord. Histologically, it is characterized by bizarre giant cells coexisting with areas of typical ependymoma (1-3).
The differential diagnosis of giant cell ependymoma includes not only anaplastic ependymoma and other glial lesions (pleomorphic xanthoastrocytoma and giant cell astrocytoma), but also non-glial neoplasms that may show bizarre tumor cells, including schwannoma, fibrous histiocytoma, metastatic carcinoma and metastatic melanoma.
This case did not satisfy the WHO criteria for anaplastic ependymoma, due to the absence of increased cellularity, brisk mitotic activity, microvascular proliferation and pseudopalisading necrosis. Features inconsistent with pleomorphic xanthoastrocytoma include this tumor's infratentorial location, scarce reticulin pattern and the absence of intracellular lipidic material. Giant cell astrocytoma is associated with tuberous sclerosis, and has cells resembling ganglion cells (4). Schwannomas are S100 positive and GFAP negative. Melanomas are positive for HMB45 and MelanA and metastatic carcinoma is positive for keratins (5,6).
Despite the apparent anaplastic appearance, giant cell ependymoma usually shows a behavior similar to other WHO grade II ependymomas. This patient was disease free 18 months post-surgery.
1. Szpak GM, Lewandowska E, Schmidt-Sidor B, Pasennik E, Modzelewska J, Stepien T, Zdaniuk G, Kulczycki J, Wierzba-Bobrowicz T. Giant cell ependymoma of the spinal cord and fourth ventricle coexisting with syringomyelia. Folia Neuropathol 2008;46:220
2. Barbagallo GM, Caltabiano R, Parisi G, Albanese V, Lanzafame S. Giant cell ependymoma of the cervical spinal cord: case report and review of the literature. Eur Spine J 2009;18 Suppl 2:186
3. Shintaku M, Sakamoto T. Tanycytic ependymoma of the filum terminale with pleomorphic giant cells. Brain Tumor Pathol 2009;26:79
4. Takei H, Adesina AM, Powell SZ. Solitary subependymal giant cell astrocytoma incidentally found at autopsy in an elderly woman without tuberous sclerosis complex. Neuropathology 2009;29:181
5. Tay A, Scheithauer BW, Cameron JD, Myhre MJ, Boerner MJ. Retinal ependymoma: an immunohistologic and ultrastructural study. Hum Pathol 2009;40:578
6. Ertan Y, Sarsik B, Ozgiray E, Kitis O, Dalbasti T, Akalin T. Pigmented ependymoma with signet-ring cells and Rosenthal fibers: a rare variant of ependymoma. Neuropathology 2010;30:71
7. Mahfouz S, Aziz AA, Gabal SM, el-Sheikh S. Immunohistochemical study of CD99 and EMA expression in ependymomas. Medscape J Med 2008;10:41
CNS tumor chapter of PathologyOutlines.com.
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