[Epithelioid angiomyolipoma of the kidney--a new tumor entity. Case report on a tumor with many multinucleated giant cells].

Epithelioid angiomyolipoma is a recently recognized tumor entity, of which 9 tumors are documented in the literature. We report a case that occurred in a 19 years old patient. The tumor consisted of epithelioid cells ranging from medium sized and polygonal to giant cells with prominent nucleoli. Remarkably, there were many multinucleated giant cells. Hemorrhage, necrosis, and clusters of foamy macrophages were also present. Obvious elements of typical angiomyolipoma, especially fatty tissue was not found. Flow cytometry revealed diploid tumor cells with a high S-phase fraction of 9.7%. Melanoma-associated antigen HMB-45 and CD 68 was detected in the epithelioid and spindle cells. The multinucleated giant cells stained for desmin and KP1, and to a lesser extent for HMB-45 and vimentin. There was no expression of cytokeratin or epithelial membrane antigen. Epithelioid angiomyolipoma often pose problems in diagnosis, particularly with regard to distinction from renal cell carcinoma. Previous reports in the literature suggest that epithelioid angiomyolipoma may have malignant potential.