摘要目的 探讨内淋巴囊肿瘤(ELST)的临床病理学特征、免疫表型及其诊断与鉴别诊断。方法 分析5例ELST的临床和病理形态学特点，以EnVision二步法用波形蛋白、角蛋白(AE1/AE3)、CK8/18、CK5/6、上皮细胞膜抗原(EMA)、胶质纤维酸性蛋白(GFAP)、S-100蛋白、突触素、癌胚抗原(CEA)、甲状腺转录因子-1（TTF-1）、血管内皮生长因子(VEGF)、D2-40、Calponin、Calretinin、Ki-67等抗体进行免疫组织化学标记，取2例尸检正常内淋巴囊及8例桥脑小脑角区脉络丛乳头状瘤做对比观察。结果 ELST患者发病年龄23 ～ 35岁，男性2例，女性3例。首发症状有耳鸣、耳痛、听力下降、耳出血及流液，2例伴有头痛。病史半年至10年，其中3例有复发。影像学检查肿物位于桥脑小脑角区，伴有岩骨骨质广泛破坏。组织学改变：肿瘤呈乳头状及腺样结构，乳头被覆瘤细胞单层排列，瘤细胞界限清楚，胞质嗜酸或透明，胞核异型性不大，居中或偏向于腔面，可见扩张的腺样结构，其内有嗜酸性的胶样物质，纤维性间质中血管丰富，小血管紧贴于上皮下，5例均有硬膜或骨质内浸润。免疫组织化学标记：5例ELST的AE1/AE3、CK8/18、CK5/6及VEGF阳性，4例EMA阳性，3例Calponin局灶阳性，2例S-100蛋白局灶阳性，2例波形蛋白阳性，1例GFAP局灶阳性，1例突触素局灶弱阳性，5例CEA、TTF-1、D2-40、Calretinin均为阴性，5例CD34血管阳性，5例Ki-67阳性指数均＜1％。8例脉络丛乳头状瘤的突触素均为阳性，7例S-100蛋白阳性，2例GFAP阳性，1例D2-40阳性，4例AE1/AE3阳性，5例CK8/18阳性,8例EMA、CK5/6及Calponin均为阴性。结论 ELST很少见，其易侵袭骨质，有复发倾向，WHO中枢神经系统肿瘤分类为低度恶性，其最应与桥脑小脑角区的脉络丛乳头状瘤进行鉴别。不同的临床影像特点、组织形态及免疫组织化学染色可以鉴别。

abstractsObjectiveTo study the clinicopathologic features and immunophenotype of endolymphatic sac tumor (ELST) and normal endolymphatic sac. Methods The clinical and histologic features were evaluated in 5 cases of ELST. Eight cases of choroid plexus papilloma at cerebellopontine angle and 2 cases of normal endolymphatic sac were used as controls. Immunohistochemical study for vimentin,AE1/AE3, CK8/18, CK5/6, EMA, GFAP, synaptophysin, S-100 protein, CEA, TTF-1, VEGF, D2-40,calponin, calretinin and Ki-67 was carried out. Results The age of onset of ELST ranged from 23 to 35years ( median =24 years ). The male-to-female ratio was 2 ∶ 3. The clinical presentation was tinnitus,otalgia, hearing loss, otorrhagia with effusion and headache. The duration of symptoms ranged from 6 months to 10 years. Local recurrences were noted in 3 cases. Radiologically, the tumors were located at cerebellopontine angle and demonstrated petrous bone destruction. Histologic examination showed that the tumors had a papillary-glandular pattern. The papillae were covered by a single layer of low cuboidal cells. The tumor cells had distinct cell borders and contained eosinophilic to clear cytoplasm. The nuclei were slightly atypical and sometimes apically located. Focal dilated glandular structures with colloid-like material were also identified. The surrounding stroma was vascularized. All of the 5 cases had dural or petrous bone infiltration. Immunohistochemical study showed that all of the 5 cases were positive for AE1/AE3, CK8/18,CK5/6 and VEGF, 4 cases for EMA, 3 cases for calponin (focal) , 2 cases for vimentin, 2 cases for S-100protein, 1 case for GFAP and 1 case for synaptophysin (focal and weak). The Ki-67 index measured less than 1％. The staining for D2-40, calretinin, CEA and TTF-1 was negative. The 2 cases of the normal endolymphatic sac were positive for AE1/AE3 and CK8/18, and negative for CK5/6, EMA, S-100 protein,GFAP and synaptophysin. The 8 cases of choroid plexus papilloma were positive for synaptophysin. Seven cases were also positive for S-100 protein, 2 cases for GFAP and 1 case for D2-40. All of the 8 cases were negative for EMA, CK5/6 and calponin. Conclusions ELST is a rare slow-growing and potentially malignant tumor with a tendency of bone invasion and local recurrence. Distant metastasis is not observed. It must be distinguished from choroid plexus papilloma occurring at cerebellopontine angle. Correlation with clinical, radiologic and immunohistochemical findings would also be helpful.