EXTRARENAL ANGIOMYOLIPOMA WITH MELANOCYTIC AND HIBERNOMA-LIKE FEATURES

Angiomyolipoma is a tumor commonly occurring in the kidney, but occasi onally found in extrarenal sites. Retroperitoneal angiomyolipoma with unusual features presenting in a 39 year old woman with hypertension i s reported in this paper. Tumor fat was inconspicuous, and present lar gely as hibernoma-like microvesicular lipid. Tumor cells also demonstr ated positivity for HMB-45 and S-100 protein, and by electron microsco py showed occasional cytoplasmic striated granules indistinguishable f rom stage II premelanosomes. However, electron microscopy and immunocy tochemistry also confirmed the presence of a substantial myogenous com ponent in the tumor, establishing the diagnosis of angiomyolipoma. The implications of these findings, and the role of immunocytochemistry a nd electron microscopy in the diagnosis of this tumor are discussed.