Image Description
Angiomyolipomas with a predominance of spindled smooth muscle cells may be mistaken for a leiomyoma, leiomyosarcoma, or a gastrointestinal stromal tumor. In such cases, the presence of islands of mature fat and aggregates of epithelioid cells with clear cytoplasm (perivascular epithelioid cell) adjacent to the vessel walls are helpful diagnostic clues. Primary smooth muscle tumors of kidney are extremely rare. Immunohistochemical staining for melanocytic markers should be performed on all such cases.