Two Thymomas of Different Histological Subtypes Arising in a Giant Thymolipoma: Case Report and Review of the Literature.

Thymolipoma is a rare benign tumor of the anterior mediastinum. Only a few reports describing thymoma arising within a thymolipoma have been documented in the literature. We report herein a detailed description of thymolipoma giving rise to 2 thymomas of different histological subtypes. A 74-year-old male with history of metastatic papillary thyroid carcinoma gradually developed 2 soft tissue nodules within a large right hemithorax fatty mass that was present for the past 20 years. Computed tomography (CT)-guided needle biopsy revealed one of the soft tissue nodules to be a thymoma, and the entire mass was surgically resected. Final pathological examination demonstrated the mass to be a thymolipoma containing a micronodular thymoma with lymphoid stroma as well as a WHO type B1 thymoma. No evidence of disease recurrence was seen at the time of his 7-year follow-up. This case documents a rare presentation of thymolipoma harboring 2 thymomas of different histological subtypes and highlights the need for early surgical resection of thymolipomas, as they may harbor malignant nodules.