Thymolipoma, report of a case suggesting an origin from thymic true hyperplasia

The authors describe a rare case of thymolipoma in a 26-year-old, otherwise healthy woman presenting with general fatigue. Radiological examinations disclosed a large anterior mediastinal mass. Macroscopically, the resected tumor was approximately 5 × 10 cm², with nodular configuration, and microscopically, 3 components were identified: a normal thymic rim, hyperplastic thymic tissue, and a typical thymolipomatous component at the periphery of the hyperplastic area. The predominant component of the tumor was hyperplastic thymic tissue. The tumor was diagnosed as thymolipoma at the initial stage of development. This case suggests the histogenesis of thymolipoma-fatty regression or infiltration of fatty tissue into a previously hyperplastic thymus.