化生性胸腺瘤三例临床病理分析

Clinicopathologic analysis of 3 patients with metaplastic thymoma

目的探讨化生f生胸腺瘤的临床病理特点。方法应用免疫组织化学方法观察3例化生性胸腺瘤的组织学特点及免疫学表型，并复习相关文献。结果3例患者中，女性2例，男性1例，年龄分别为45、52、40岁。所有肿瘤显示双相分化特点，上皮细胞区域与梭形细胞区域交错分布并相互移行。上皮细胞呈相互吻合的束状、岛状及宽大的梁状排列，细胞轻度异型，可见核沟及核内假包涵体，偶见核分裂象；梭形细胞呈短束状或席纹状排列，细胞温和，未见核分裂象。免疫表型：上皮细胞区域AE1／AE3呈强阳性表达，梭形细胞区域表达Vimentin，两种区域中Ki-67指数均〈5％。结论化生性胸腺瘤是一种罕见的胸腺肿瘤，属低度恶性肿瘤，偶尔有肿瘤侵犯邻近组织和复发，完整切除肿瘤预后良好，诊断依靠病理组织学和免疫组织化学标记。

Objective To investigate the clinicopathologic characteristics of metaplastic thymoma. Methods The histological features and immunophenotype of three cases with metaplastic thymoma were studied, and the literatures were reviewed. Results There were 2 females and 1 male of 3 patients with 45, 52 and 40 years old, respectively. All tumors were characterized by a biphasic pattern composed of epithelial components and spindle cells. The epithelial areas consisted of anastomosing cords and islands or broad trabeeulae of cohesive neoplasia cells. Some epithelial cells showed mild cytologic atypia, the presence of prominent nuclear grooves or pseudoinclusion body, and very low mitotic activity. The cells appeared bland and a fine nuclear chromatin pattern, and the mitoses were not found. The epithelial cells were diffusely and strongly positive for AE1/AE3. The spindle cells were diffusely positive for Vimentin. The Ki-67 fraction was low （〈5 %） in both components. Conclusions Metaplastie thymoma is a rare primary thymic epithelial tumor, and its biologic behavior is likely benign or lowly malignant process. Occasionally, the tumor invades adjacent tissue or recurrence. With complete tumor resection, the patients have good prognosis. The diagnosis of metaplastic thymoma mainly relies on its morphologic features and immunohistoehemical profiles.