2025 Volume 42 Issue 2 Pages 132-138
A metaplastic thymoma is a rare thymic neoplasm. A 92-year-old woman underwent resection of an anterior mediastinal tumor. Histopathological findings showed a biphasic pattern of polygonal epithelioid and spindle cells. The epithelioid cells were characterized by cellular atypia, including enlarged nuclei, irregular nuclear shapes, and increased chromatin content. The two cellular components showed areas of transition, and cellular atypia was also observed in some spindle cells. Based on histopathological and immunohistochemical findings, the patient was diagnosed with metaplastic thymoma. Although cellular atypia has been reported in metaplastic thymomas, it is usually confined to epithelioid cells, and cellular atypia in spindle cells is uncommon. Metaplastic thymomas are rarely encountered in routine practice;therefore, pathologists should be familiar with the variability of their histologic features.
