Purpose To investigate the clinicopathological features, diagnosis and differential diagnosis of endolymphatic sac tumor. Methods Clinical data of 2 cases of endolymphatic sac tumor that was misdiagnosed as choroids plexus papilloma and papillary hidra-denoma were analyzed, and the morphological features were observed by light microscopy and immunohistochemistry. Results Two male patients displayed symptoms of progressive hearing loss, bleeding or suppurating in external auditory canal. Imaging displayed cystic - solid lesions in temporal bone and permeatal destruction of bone. Microscopically, the tumors showed a papillary and glandular architecture lined by a single layer of cuboidal-to-columnar cells, with a fibrous and vascular core. Eosinophilic colloid matter accumulated in the lumen of gland. Hemorrhage and cholesterol crystal could be found in the stroma with abundant collagen. Immunohisto-chemical staining revealed that tumor cells were positive for CK, EMA, CK7, CK19, NSE, CD56 and vimentin, negative for GFAP, TTF-1, CEA, TG, Galectin-3, CD10, Syn and CgA. The proliferating index of Ki-67 was low. Conclusions Endolymphatic sac tumor is a rare and locally aggressive low-grade neoplasm, easily being confused with other tumors by clinicians and pathologists. The diagnosis and differential diagnosis rely mainly on histopathological and immunohistochemical findings, combined with the special location.%目的 探讨内淋巴囊肿瘤(endolymphatic sac tumor,ELST)的临床及病理形态特点,诊断及鉴别诊断要点,提高对其认识.方法 收集2例分别被误诊为脉络丛乳头状瘤及生乳头状汗腺瘤的ELST的临床资料,重新切片行HE染色及免疫组化标记.结果 2例均为男性,以进展性耳聋,外耳道流血或流脓为主要症状.影像学提示颞骨岩部囊实性占位并周围骨质破坏.病理形态特征:肿瘤呈弥漫囊性乳头状结构,乳头表面被覆单层立方或高柱状上皮细胞,轴心为纤维血管组织;部分区域乳头间纤维间质中见腺体结构并囊性扩张,腺腔内可见均质红染的胶样物质.间质纤维组织增生、玻璃样变,见含铁血黄素沉积及胆固醇结晶.免疫组化结果示2例病变肿瘤细胞均表达CK、EMA、CK7、CK19、NSE、CD56和vimentin;其中1例S-100阳性;而GFAP、TTF-1、CEA、TG、Galectin-3、CD10、Syn及CgA均阴性,Ki-67增殖指数低.结论 ELST为罕见的低度恶性肿瘤,临床及病理学特征均易与其他肿瘤混淆.病理组织学形态及免疫组化标记是诊断及鉴别诊断的依据,同时需结合患者特殊发病部位.
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