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Canine Ependymoma: Diagnostic Criteria and Common Pitfalls

Miller, A D; Koehler, J W; Donovan, T A; Stewart, J E; Porter, B F; Rissi, D R; Priestnall, S L; Schulman, F Y


A D Miller

J W Koehler

T A Donovan

J E Stewart

B F Porter

D R Rissi

S L Priestnall

F Y Schulman


Reports of canine ependymoma are generally restricted to single case reports with tumor incidence estimated at 2% to 3% of primary central nervous system (CNS) tumors. While most commonly reported in the lateral ventricle, tumors can occur anywhere in the ventricular system and in extraventricular locations. Rosettes and pseudorosettes are a common histologic feature; however, these features can be mimicked by other CNS neoplasms. Thirty-seven potential ependymoma cases were identified in a retrospective database search of 8 institutions, and a histologic review of all cases was conducted. Of 37 cases, 22 candidate cases were further subjected to a consensus histologic and immunohistochemical review, and only 5 of 37 (13.5%) were conclusively identified as ependymoma. The neuroanatomic locations were the lateral ventricle (3/5), third ventricle (1/5), and mesencephalic aqueduct (1/5). Subtypes were papillary (4/5) and tanycytic (1/5). Histologic features included rosettes (5/5), pseudorosettes (5/5), ependymal canals (2/5), tanycytic differentiation (1/5), blepharoplasts (1/5), ciliated cells (1/5), and high nuclear to cytoplasmic ratio (5/5). Immunolabeling for GFAP (4/4) and CKAE1/3 (3/4) was found in pseudorosettes, rosettes, and scattered individual neoplastic cells. Diffuse but variably intense cytoplasmic S100 immunolabeling was detected in 3 of 4 cases. Olig2 intranuclear immunolabeling was observed in less than 1% of the neoplastic cells (3/3). Tumors that had pseudorosettes and mimicked ependymoma included oligodendroglioma, choroid plexus tumor, pituitary corticotroph adenoma, papillary meningioma, and suprasellar germ cell tumor. These findings indicate that canine ependymoma is an extremely rare neoplasm with histomorphologic features that overlap with other primary CNS neoplasms.


Miller, A. D., Koehler, J. W., Donovan, T. A., Stewart, J. E., Porter, B. F., Rissi, D. R., …Schulman, F. Y. (2019). Canine Ependymoma: Diagnostic Criteria and Common Pitfalls. Veterinary Pathology, 56(6), 860-867.

Journal Article Type Article
Acceptance Date Jul 1, 2019
Publication Date Jul 2, 2019
Deposit Date Aug 2, 2019
Publicly Available Date Jul 2, 2020
Print ISSN 0300-9858
Publisher American College of Veterinary Pathologists
Peer Reviewed Peer Reviewed
Volume 56
Issue 6
Pages 860-867
Public URL


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