伴淋巴样间质微结节型胸腺瘤6例临床病理分析

Micronodular thymoma with lymphoid stroma: a clinicopathologic study of 6 cases

目的探讨伴淋巴样间质微结节型胸腺瘤的临床病理学特征。方法回顾性分析6例伴淋巴样间质微结节型胸腺瘤的临床病理学形态及免疫表型特征,并复习相关文献。结果 6例患者中男性4例,女性2例;平均年龄65岁;所有病例均不伴重症肌无力,胸部CT诊断为胸腺肿瘤。病理组织学:6例中4例合并其他类型肿瘤,包括B1型胸腺瘤(1例)、A型胸腺瘤(2例)和肺腺癌(1例)。伴淋巴样间质微结节型胸腺瘤病理组织形态相似,均表现为上皮样肿瘤细胞呈微结节状或融合成片状生长,分布于富淋巴细胞的间质中。免疫表型显示肿瘤细胞表达CKpan、CK5/6、p63;淋巴细胞表达TdT、CD3、CD5、CD20;其中2例EBER原位杂交检测阴性。5例随访,未见复发或转移。结论伴淋巴样间质微结节型胸腺瘤是一种少见的肿瘤,好发于前纵隔,可发生于异位颈部,该肿瘤与其他类型胸腺瘤相似,肿瘤细胞呈微结节状散在分布于富淋巴细胞的间质为其特征,淋巴细胞除表达Td T以外,也有CD20表达;此外,该肿瘤可伴发A型/B1型胸腺瘤、甚至肺腺癌。病理诊断时需与微小胸腺瘤、A型/AB型胸腺瘤及淋巴上皮癌鉴别。

Purpose To explore the clinicopathological features of micronodular thymoma with lymphoid stroma. Methods The clinicopathological data and immunohistochemical staining of the tumor of the 6 cases with micronodular thymoma with lymphoid stroma were analyzed and review of the literatures. Results There were 4 males and 2 females with average age of 65 years old. Clinically,all cases were not associated with myasthenia gravis and the thymic tumors were detected by the chest computed tomography. Histopathology,there were 4 cases with other types of tumors,including type B1 thymoma（1 case）,type A thymoma（2 cases） and a case with adenocarcinoma of lung. All micronodular thymomas with lymphoid stroma showed similar histologic changes. It was characterized that epithelial tumor cells showed micronodular or sheet-like areas pattern with an abundant lymphoid stroma. The immunohistochemical staining was showed that the epithelioid tumor cells were positive for CKpan,p63 and CK5/6,lymphocytes were positive for CD3,Td T,CD5 and CD20. However,it was negative for EBER at 2 cases with micronodular thymoma with lymphoid stroma by hybridization in situ detection. 5 cases have follow-up data and no recurrence or metastasis. Conclusion Micronodular thymoma with lymphoid stroma is a rare tumor,which mainly locate in the anterior mediastinum,occasionally in the cervical ectopic. Histologically, the micronodular thymoma with lymphoid stroma is similar to other types of thymoma. The tumor cells demonstrated micronodular growth pattern and were separated by an abundant lymphoid stroma. The lymphocytes within the tumor stroma were specifically positive for Td T and CD20. Furthermore,the micronodular thymoma with lymphoid stroma may be combined with type A or B1 thymoma,even along with lung adenocarcinoma. It is necessary to differentiate micronodular thymoma with lymphoid stroma from type A or AB thymoma,lymphatic epithelial carcinoma and microscopic thymoma.