HMB-45

HMB-45 is a monoclonal antibody that reacts against an antigen present in melanocytic tumors such as melanomas, and stands for human melanoma black 45. It is used in anatomic pathology as a marker for such tumors. The specific antigen recognized by HMB-45 is now known as Pmel 17.

HMB-45 was discovered by Drs. Allen M. Gown and Arthur M. Vogel in 1986. The antibody was generated to an extract of melanoma. It reacts positively against melanocytic tumors but not other tumors, thus demonstrating specificity and sensitivity.

In a study to determine diagnostic usefulness of specific antibodies used to identify melanoma, HMB-45 had a 92% sensitivity when used to identify melanoma. The antibody also reacts positively against junctional nevus cells and fetal melanocytes.

Despite this relatively high sensitivity—HMB-45 does have its drawbacks. HMB-45 can be detected in only 50-70% of melanomas. HMB-45 does not react well against intradermal nevi, normal adult melanocytes, spindle cell melanomas and desmoplastic melanomas. HMB-45 is nonreactive with almost all non-melanoma human malignancies, with the exception of rare tumors showing evidence of melanogenesis (e.g., pigmented schwannoma, clear cell sarcoma) or tumors associated with tuberous sclerosis complex (angiomyolipoma and lymphangiomyoma).