摘要目的 探讨CD20在胸腺瘤中的表达及其临床和病理学意义.方法 对179例手术切除的胸腺肿瘤病例,按照2004年的WHO分类标准并结合临床病理资料,重新进行病理组织学分类,并选取其中资料完整的102例肿瘤组织,运用免疫组织化学EnVision法分别标记CD20、CKpan、末端脱氧核苷酸转移酶、CD3、CD5、CD43、CD99、S-100蛋白.其中重点观察肿瘤性上皮细胞及背景淋巴细胞的CD20表达特征,其他指标用以标记细胞.同时将所有病例按是否伴有重症肌无力分为两组,对结果进行统计学分析.结果 102例胸腺瘤中,A型7例、AB型32例、B1型17例、B2型15例、B3型17例,胸腺癌14例,CD20表达于肿瘤性上皮细胞,在A、AB、B1、B2、B3型胸腺瘤和胸腺癌中的阳性率分别为3/7、84.4%(27/32)、1/17、2/15、0/17、0/14.肿瘤的背景淋巴细胞的阳性率分别为3/7、18.8%(6/32)、14/17、11/15、11/17、6/14.伴重症肌无力组(40例)肿瘤内淋巴细胞的CD20阳性表达率为67.5%(22/40),不伴重症肌无力组(62例)阳性表达率为35.5%(22/62),CD20阳性的B淋巴细胞主要分布于伴重症肌无力组,两组间差异有统计学意义(P＜0.05).结论 A型、AB型和极少数的B1、B2型胸腺瘤的上皮细胞均具有表达CD20蛋白的特征,这类上皮细胞属于肿瘤性上皮;而B3型胸腺瘤及胸腺癌的肿瘤性上皮细胞缺乏表达CD20蛋白的特征.胸腺瘤伴重症肌无力者,肿瘤内B淋巴细胞增生,数量明显多于不伴重症肌无力者.AB型胸腺瘤并非A型与B型胸腺瘤的单纯混合,可能属于不同的细胞起源而表现出不同的组织形态和免疫表型.

abstractsObjective To study the expression of CD20 in thymomas and its clinical significance.Methods One hundred and seventy-nine cases of thymoma were enrolled into the study. The histologic diagnosis was reviewed by two experienced pathologists on the basis of the 2004 WHO classification. One hundred and two cases were selected for immunohistochemical study for CD20, pancytokeratin, TdT, CD3,CD43, CD99 and S-100 protein. The cases were further categorized into two groups, according to the association with clinical evidence of myasthenia gravis. The immunostaining pattern was then statistically analyzed. Results Amongst the 102 cases studied, 7 cases belonged to type A thymoma, 32 cases type AB thymoma, 17 cases type B1 thymoma, 15 cases type B2 thymoma, 17 cases type B3 thymoma and 14 cases thymic carcinoma. The expression rates of CD20 in neoplastic epithelial cells of type A, type AB, type B1,type B2 and type B3 thymomas and thymic carcinomas were 3/7,84.4% (27/32), 1/17, 2/15, 0/17, 0/14, respectively. The proportions of CD20-positive lymphocytes in the background were 3/7,18.8% (6/32), 14/17,11/15,11/17,6/14, respectively. The proportion of CD20-positive intra-tumoral B lymphocytes in the group of thymomas with myasthenia gravis was 67.5% (22/40) , in contrast to 35. 5% (22/62) in those without myasthenia gravis. Conclusions The neoplastic epithelial cells in cases of type A and type AB thymoma, as well as few cases of type B1 and B2 thymoma, express CD20. The immunostain highlights the presenc e of oval, stellate or spindly cells. Thymomas associated with myasthenia gravis contain a significant population of CD20-positive intra-tumoral B lymphocytes. Type AB thymomas may be originated from different populations of cells, rather than a simple admixture of type A and B thymoma cells.