目的　探讨复合型胸腺瘤 (AB +B)的病理学和生物学特性及其临床病理学意义。方法根据WHO“胸腺肿瘤的组织学分型” ,对 141例胸腺上皮肿瘤结合临床和随访资料进行统计学分析 ,对其中的AB +B型胸腺瘤的临床和组织病理学特征进行描述。结果　胸腺瘤A型 7例 (5 0 % ) ,AB型 48例 (34 0 % ) ,AB +B型胸腺瘤 14例 (9 9% ) ,B1型 9例 (6 4% ) ,B2型 2 2例 (15 6 % ) ,B3型 2 1例(14 9% ) ,C型 2 0例 (14 2 % ) ,组织学类型与预后的相关性非常显著。复合型 (AB +B)胸腺瘤具有较明确的组织病理学特征 ,其预后特性介于A、AB型与B1～B3型之间 ,差异有显著性 (logrank :χ2 =48 18,P <0 0 0 1)。临床Ⅰ期 :73例 (5 1 8% ) ,Ⅱ期 :16例 (11 3% ) ,Ⅲ期 :44例 (31 2 % ) ,Ⅳ期 8例(5 7% )。病理类型与临床分期呈正相关 ,有非常显著的统计学意义 (logrank :χ2 =71 30 ,P <0 0 0 1)。AB +B型胸腺瘤归入胸腺瘤Ⅱ级 ;胸腺瘤分级与预后呈正相关 (logrank :χ2 =5 7 49,P <0 0 0 1)。结论　复合型胸腺瘤 (AB +B)具有较明确的组织病理学特征 ,其病理学和生物学特性与良、恶性胸腺瘤有显著性差异 ,介于良恶性之间 ,建议称之为交界性胸腺瘤 Objective To investigate the pathological and biological characteristics of composite thymoma (AB + B) and its clinicopathological significance. Methods The clinical and follow-up data of 141 cases of thymic epithelial tumor were analyzed according to WHO histological classification of thymus tumors, and the clinical and histopathological features of AB + B thymoma were described. Results There were 7 cases (50%) of thymoma type A, 48 (34%) AB type, 14 (9 9%) AB type B thymoma, 9 (6 4%) type B1 and 2 2 cases (15 6%), B3 type 21 cases (14 9%), C type 20 cases (14 2%), histological type and prognosis of the correlation is very significant. The composite (AB + B) thymoma had definite histopathological features, and the prognosis was between A and AB and B1 to B3 (logrank: χ2 = 48 18, P <0 0 0 1). There were 73 cases (51.8%) in stage Ⅰ, 16 cases (11 3%) in stage Ⅱ, 44 cases (31 2%) in stage Ⅲ and 8 cases (5 7%) in stage Ⅳ. There was a positive correlation between pathological type and clinical stage (logrank: χ2 = 71 30, P <0.01). AB + B thymoma was classified as grade II thymoma; thymoma grade was positively correlated with prognosis (logrank: χ2 = 5 7 49, P <0 0 01). Conclusions The composite thymoma (AB + B) has definite histopathological features. The pathological and biological characteristics of the complex thymoma are significantly different from that of benign and malignant thymoma, which is between benign and malignant. It is suggested that the borderline Thymoma