Angiomyolipomas: the nature and expression of the HMB45 antigen.

Fifteen cases of angiomyolipoma (AML) were studied by the immunoperoxidase method to investigate the nature of the HMB45 antigen and to determine if the antigen that stains with HMB45 in AML is the same HMB45 antigen that stains melanoma cells. Other antibodies utilized to accomplish this study included vimentin, cytokeratin, S-100 protein, and muscle actin (HHF-35). Large interstitial cells of AML regularly react with two different sources of HMB45 and are often positive for vimentin. The HMB45 reactivity of both antibodies is abolished by pretreating the tissue with neuraminidase. The same cells are not immunoreactive with cytokeratin or S-100 protein. A subpopulation of cells in AML demonstrates coexpression of HMB45 and muscle-specific antigen by double-immunolabeling techniques. These results suggest that the AML antigen that reacts with HMB45 is the same antigen present in melanocytic/melanoma cells and that a pluripotent cell, which generates a divergent range of differentiation, may be involved in the genesis of AMLs.