A Case of Metaplastic Thymoma

Abstract

Metaplastic thymoma is a rare, biphasic, thymic epithelial tumor consisting of a mixture of polygonal cell components and spindle cell components. A case of metaplastic thymoma treated with surgery is reported along with a review of the relevant literature. The patient was a 69-year-old woman in whom abnormal right hilar shadow was seen on chest X-ray during a medial checkup. Chest computed tomography (CT) showed an irregularly shaped, 80 mm×69 mm×36 mm tumor with a solid, heterogeneous interior in the anterior mediastinum. Positron emission tomography-CT (PET-CT) showed high accumulation, with an SUVmax of 10.2 A thymic tumor was diagnosed, and the thymus was resected with the surrounding fat tissue by performing a median sternotomy. The resected sample was an encapsulated 8 cm×6 cm tumor, and its cut surface was uniformly yellowish-white and solid. Pathological findings included a mixture of polygonal cell components and spindle cell components, with a well-defined border. AE1/AE3 and E-cadherin were strongly positive in the epithelial components composed of polygonal cells, while vimentin was positive in the spindle cell components. The patient was diagnosed with biphasic, metaplastic thymoma showing polygonal cell and spindle cell components.