Objective: To investigate the clinicopathologic characteristics of metaplastic thymoma. Methods: Two cases of metaplastic thymoma were studied histologically and immunohistochemically and the literatures were reviewed. Results: There were 2 male of patients with age of 55 and 56 respectively. Microscopically, 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 and the presence of prominent nuclear grooves or psedoinclusion, yet mitotic activity was very low. The cells were bland appearing with a fine nuclear chromatin pattern and mitoses were not found. Immunohistochemically, the epithelial cells were diffusely and strongly positive for CK19 and AE1/ AE3. The spindle cells were diffusely positive for Vimentin, BCl-2 and CD99. Two kinds of cells were focally and weakly positive for AE1/AE3 and epithelial membrane antigen (EMA). The Ki67 fraction was low (<5%) in both components. The scanty stromal small lymphocytes cells displayed a mature immunophenotype positive for CD3, CD5 and CD20 and negative for teminal deoxynucleotidyl transferase (TdT) and CD99. Conclusion: Metaplastic thymoma is a rare primary thymic epithelial tumor, and its biologic behavior is likely benign or lowly malignant process. The diagnosis of metaplastic thymoma mainly relies on its morphologic features and immunohistochemical profiles. Surgical excision alone is recommended.