Komori Kenjiro, Tsubochi Hiroyoshi, Ohno Keisuke, Minegishi Kentaro, Endo Shunsuke
Department of Thoracic Surgery, Jichi Medical Univergity Saitama Medical Center, Saitama, Japan.
Kyobu Geka. 2021 Mar;74(3):241-243.
Metaplastic thymoma is a rare histologic variant of thymic epithelial tumors and is characterized by a biphasic growth pattern. We herein report the case of 44-year-old woman who underwent surgery for metaplastic thymoma. Computed tomography scan revealed a well-circumscribed mediastinal tumor: 56 mm in diameter with homogenous enhancement. The tumor was suspected to be a non-invasive thymoma, and thymomectomy with resection of the surrounding thymus was performed using thoracoscopy. The resected tumor measured 60 mm and was grossly well-encapsulated. The cut surface was gray to white and homogenous. Microscopically, the epithelial components took the form of an anastomosing nest to broad trabeculae intertwining with the bundle of spindle cells. Mitosis was not found and the Ki-67 index was < 1%. Cytokeratin 5/6 was strongly positive in the epithelial components composed of polygonal cells. Terminal deoxynucleotidyl transferase positive immature T cells were not observed. Based on these pathologic findings, the tumor was identified as metaplastic thymoma.
化生性胸腺瘤是胸腺上皮肿瘤中一种罕见的组织学亚型，其特征为双相生长模式。我们在此报告一例44岁接受化生性胸腺瘤手术的女性病例。计算机断层扫描显示一个边界清晰的纵隔肿瘤：直径56毫米，强化均匀。该肿瘤疑似为非侵袭性胸腺瘤，遂采用胸腔镜行胸腺瘤切除术并切除周围胸腺。切除的肿瘤大小为60毫米，大体上包膜完整。切面呈灰白色，质地均匀。显微镜下，上皮成分呈相互吻合的巢状至宽阔小梁状，与梭形细胞束相互交织。未见有丝分裂，Ki-67指数<1%。细胞角蛋白5/6在由多边形细胞组成的上皮成分中呈强阳性。未观察到末端脱氧核苷酸转移酶阳性的未成熟T细胞。基于这些病理表现，该肿瘤被确诊为化生性胸腺瘤。
