HMB-45 recognizes stimulated melanocytes.

A monoclonal antibody (HMB-45) was previously reported to bind to melanoma cells, and the junctional component of nevus cells, but not to normal adult melanocytes. We have tested HMB-45 binding in several conditions under which melanocyte stimulation might be expected in adults, i.e. 3 simple lentigines, 2 solar lentigines, 7 recent surgical scars (from re-excision of non-melanocytic tumors), 2 surgical scars from re-excisions of melanomas (after complete primary excisions), 9 hemangiomas from non-sun-exposed skin, 1 basal cell carcinoma, 1 acute ecchymosis, 1 keloid, and 1 dermatofibroma. Positive controls included 6 malignant melanomas and 1 fetal skin sample. Melanocytes were strongly positively stained overlying hemangiomas, within or near recent surgical scars of melanocytic and non-melanocytic tumor re-excisions, near basal cell carcinoma, and in fetal skin. Melanocytes either were not stained or were stained only focally for trace amounts in the normal skin near the new margins of the wide re-excision specimens for melanoma, i.e., at a distance from the scar, in the simple lentigines and in the fibrotic lesions. Thus, HMB-45 is staining an antigen which appears in adult melanocytes during stimulation and in fetal skin, as well as in melanomas. This stimulation is associated with conditions that would have increased vascularity, suggesting a melanocyte response to a plasma factor, or other endothelial cell derived factor. HMB-45 would not be a useful marker for residual melanoma cells in melanoma re-excision specimens.