[Activation of epidermal melanocytes is independent of epithelial proliferation and vascularization. Immunohistologic study using HMB-45 antibody with review of the literature].

Antibodies against HMB-45 antigen are widely used in the immunohistochemical investigation of melanocytic tumours as a marker of activation. While malignant transformation is one explanation for HMB-45 expression, we searched for other factors by investigating 252 biopsies of non-melanocytic skin lesions with 21 different diagnoses for the presence of HMB-45, using both single and double staining techniques. Epidermal melanocytes in lesions with an increased epithelial proliferation-either neoplastic or reactive-and lesions with a prominent vasculature showed an enhanced expression of HMB-45. The results indicate that the presence of HMB-45 is not only influenced by primary melanocytic changes but also may be dependent on epithelial proliferation and vascular factors. These mechanisms should be considered when interpreting HMB-45 staining of melanocytic lesions.