Clinicopathologic analysis of 3 patients with metaplastic thymoma

Abstract

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 trabeculae 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 Metaplastic 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 immunohistochemical profiles. Key words: Metaplasia; Thymoma; Immunohistochemically