摘要目的:探讨化生型胸腺瘤（metaplastic thymoma）的临床病理学特征、免疫表型、分子遗传学特征及预后。方法:收集福建省立医院2008—2019年间确诊的5例化生型胸腺瘤的临床病理学资料，行免疫组织化学染色，荧光原位杂交（FISH）检测MAML2基因，并复习相关文献。结果:男性2例，女性3例，年龄36~64岁（平均年龄52岁）。肿瘤最大径3.2~7.3 cm（平均5.1 cm）。镜下均见上皮样细胞与梭形细胞双相分化的特点，二者交错分布，可见相互移行也可见骤然过渡。形态温和，两种成分均未见核分裂象，间质见少量淋巴细胞浸润。免疫表型：上皮样成分广谱细胞角蛋白、p63及E-cadherin强阳性；梭形细胞成分波形蛋白、上皮细胞膜抗原弥漫阳性；Ki-67阳性指数均小于5%，淋巴细胞末端脱氧核苷酸转移酶阴性。FISH检测MAML2基因分离（2/4）。结论:化生型胸腺瘤属低度恶性胸腺上皮性肿瘤，诊断和鉴别诊断依赖于特征性形态学表现，必要时行免疫组织化学染色及MAML2基因检测辅助诊断，治疗以手术完整切除为主，预后良好。

abstractsObjective:To investigate the clinicopathological characteristics, immunophenotype, molecular genetic characteristics and prognosis of the metaplastic thymoma (MT).Methods:The clinicopathological and follow-up data of five MT cases were collected at Fujian Provincial Hospital from 2008 to 2019. Immunohistochemical staining and MAML2 gene detection were performed, and the relevant literature was reviewed.Results:There were 2 males and 3 females, aged 36-64 years (mean age 52 years). The tumors ranged 3.2-7.3 cm in the greatest diameter (average 5.1 cm).Microscopically, the tumor showed a biphasic pattern with epithelial cells merging gradually with the spindle cell component. The two areas transited to each other or had obvious boundary. Both components showed mild atypia. No mitosis was observed in either area, and a small number of lymphocytes were observed in the stroma. Immunohistochemical staining showed that epithelioid cells were positive for CKpan, p63 and E-cadherin. Spindle cells were positive for vimentin and EMA, while the Ki-67 index was less than 5%, and lymphocytes were negative for TdT. MAML2 gene apart signal was detected in two of the cases (2/4) that were tested by FISH.Conclusions:MT is a low-grade malignant epithelioid thymic tumor. Its diagnosis and differential diagnosis are dependent on the morphological characteristics, immunohistochemical staining and MAML2 gene detection. The primary treatment option is surgical resection, with an overall good prognosis.