(A–C). Thymic adenocarcinoma. (A) The tumor grows in a solid pattern and is comprised of polygonal tumor cells with ample cytoplasm and round nuclei (B). (C) BAP1 expression is lost in the tumor cells. Note expression of BAP1 is preserved in endothelial cells. (D–F). Thymic squamous cell carcinoma. (D) Large irregular nests of tumor cells are in a desmoplastic and fibrotic stroma. (E) The tumor cells are polygonal and have, at least in some areas, a fair amount of cytoplasm. (F) mTAP expression is lost in the tumor cells. Note the preserved expression of mTAP in endothelial and stromal cells. Magnification, H&E × 40 (A,D), × 200 (B,E), BAP1 × 200 (C), mTAP × 200 (F).