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.

中文翻译：

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犬室间隔膜瘤：诊断标准和常见误区。

犬类室管膜瘤的报告通常仅限于单例报告，其肿瘤发生率估计为原发性中枢神经系统（CNS）肿瘤的2％至3％。虽然最常见的报道是在侧脑室，但肿瘤可发生在脑室系统中和脑室外的任何地方。莲座丛和假玫瑰花are是常见的组织学特征。然而，这些特征可以被其他中枢神经系统肿瘤所模仿。在对8家机构的回顾性数据库搜索中，确定了37例潜在的室间隔膜瘤病例，并对所有病例进行了组织学检查。在37例病例中，有22例候选病例进一步接受了组织学和免疫组化的共识性检查，结果只有37例中有5例（13.5％）被确定为室间隔膜瘤。神经解剖位置是侧脑室（3/5），第三脑室（1/5）和中脑导水管（1/5）。亚型为乳头状（4/5）和单核细胞（1/5）。组织学特征包括玫瑰花结（5/5），假玫瑰花结（5/5），室管（2/5），单核细胞分化（1/5），原生质体（1/5），纤毛细胞（1/5）和高核质比（5/5）。GFAP（4/4）和CKAE1 / 3（3/4）的免疫标记被发现在假玫瑰花，玫瑰花结和散在的单个肿瘤细胞中。在4例中的3例中检测到弥漫性但强度不同的S100免疫标记。在不到1％的肿瘤细胞中观察到Olig2核内免疫标记（3/3）。具有假红斑和模仿性室管膜瘤的肿瘤包括少突胶质细胞瘤，脉络丛肿瘤，垂体皮质营养腺瘤，乳头状脑膜瘤和鞍上生殖细胞瘤。