Purpose To study the clinicopathological, immunophynotypic features of pituicytoma and its rare ependymal variant with discussion of its diagnosis and differential diagnosis. Methods 7 cases of pituicytoma, including 6 conventional pituicytomas and 1 ependymal variant tumor, were evaluated by HE staining and immunohistochemistry, and the relevant literatures were reviewed. Results Microscopically, the tumors were composed of closely packed plump spindle cells arranged in short fascicle and storiform pattern in 6 conventional pituicytomas, and whorl and papillary architecture with obvious perivascular rosette formation in the ependymal variant tumor. Immunohistochemically, all tumor cells were diffuse positive for S-100 and TTF-1, but negative for IDH1 R132H, Olig-2, CD34, NF, Syn, CgA, and pituitary hormones. Ki-67 proliferation index was less than 2％ in all cases. GFAP and EMA were only focally positive in conventional pituicytomas, whereas GFAP was diffuse positive in ependymal variant tumor with EMA dot-like staining in more than half of tumor cells. Conclusion Pituicytoma is a rare low grade glioma derived from neurohypophysis. To study helps recognition of extending morphological spectrum of pituicytoma and its new variant, which is important for its differential diagnosis consideration and clinical therapy.%目的 探讨垂体细胞瘤及其罕见的室管膜样亚型的临床病理学特征和免疫表型、诊断和鉴别诊断.方法 应用HE和免疫组化EnVision两步法染色观察7例垂体细胞瘤(6例经典型和1例室管膜样亚型)的组织学形态和免疫表型,并复习相关文献.结果 镜下6例经典型肿瘤均由致密的肥胖梭形细胞构成,瘤细胞呈短束状和车辐状排列;而1例室管膜样亚型,瘤细胞呈漩涡状和乳头状排列,伴明显的血管周菊形团结构.免疫表型:所有肿瘤均弥漫表达S-100蛋白和TTF-1,而IDH1 R132H、Olig-2、NF、CD34、Syn、CgA及垂体激素均阴性,Ki-67增殖指数均＜2％.不同的是,经典型病例GFAP和EMA仅灶阳性,室管膜样亚型中GFAP呈弥漫阳性,且＞50％瘤细胞EMA点状阳性.结论 垂体细胞瘤是起源于神经垂体细胞罕见的低级别胶质瘤,该实验有助于扩大垂体细胞瘤的形态学谱系和对新亚型的认识,对病理的鉴别诊断和临床治疗有益.
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