目的探讨胸腺瘤的分型、诊断与鉴别诊断以及治疗和预后。方法采用组织学、免疫组织化学技术对1例AB型胸腺瘤术后5年肝转移标本进行光镜观察及免疫组化标记，并结合相关文献对其临床表现、组织病理学、免疫组化特点、鉴别诊断及治疗和预后等进行综合分析。结果 AB型胸腺瘤术后5年，在肝脏组织内查见转移瘤，病理诊断为肝脏组织内转移的AB型胸腺瘤，免疫组化染色结果显示：CKpan（＋）、CD3（＋）、CD2（＋）、TdT（＋）、CD5（＋）、p53（＋）、Hep‐1（－），Ki67阳性细胞数（10％～15％）及Galectin‐3阳性表达强度高于5年前纵隔胸腺瘤。结论 AB型胸腺瘤可复发及远处器官转移，为低度恶性潜能的肿瘤， p53、Galectin‐3和Ki67的高表达可能共同影响着胸腺瘤的发生、发展和恶变过程。“,”[Objective] To explore the clinicopathological features ,histological types ,diagnosis ,differen‐tial diagnosis ,treatment and prognosis of type AB thymoma with liver metastases .[Methods]Liver metasta‐sis specimens were harvested from one 49‐year‐old female case of type AB thymoma 5 years after operation and examined histologically with light microscopy and immunohistochemistry .Comprehensive analyses were con‐ducted for clinical manifestations ,histopathology ,immunohistochemical features ,differential diagnosis ,treat‐ment and prognosis after initial operation .The pathological diagnosis for liver metastases was type AB thy‐moma .Immunohistochemical staining showed CKpan (+ ) ,CD3(+ ) ,CD2 (+ ) ,TdT (+ ) ,CD5 (+ ) ,p53 (+ ) ,Hep‐1 (-) and Ki67‐positive cells (25% ~30% ) .The expression level of galectin‐3 was higher than that in mediastinal thymoma tissue identified 5 years ago .[Conclusion]Liver metastases of type AB thymoma are extremely rare .Type AB thymoma with low malignant potential may recur and develop distant metastases . Overexpressions of p53 ,galectin‐3 and Ki67 in type AB thymoma might coordinately manipulate the process of development ,progression and malignant transformation .