Immunostaining of human melanomas by a monoclonal antibody to B700 mouse melanoma antigen

Previous studies have shown that B700, an albumin-like murine melanoma antigen, has a human homologue termed H700. Polyclonal antibodies to B700 also bind to all cultured human, swine and hamster melanoma cells, suggesting that B700 is a ''pan-melanoma'' antigen. The objects of this investigation were: (a) to determine if 2-3-3, a monoclonal antibody to B700, can be used to identify human melanomas in formalin-fixed, paraffin-embedded tissues, and (b) to determine the specificity and potential diagnostic value of 2-3-3. Forty-eight of the 49 human melanomas, including spindle melanoma cells, stained positively, as did five of the eight pigmented naevi including cellular spindle naevi. Twenty-six of the 32 human non-melanomatous lesions were negative for 2-3-3 staining (weakly positive on one breast carcinoma and positive on five neural tumours). These results indicate that 2-3-3, a monoclonal antibody to the mouse melanoma antigen B700, can be used to identify H700 in archival specimens. 2-3-3 may have an advantage over HMB45, which is the most commonly used antibody for melanoma diagnosis, because of its immunoreactivity with spindle melanocytic lesions. Antibodies to B700 may prove to be a useful adjunct in the diagnosis of human melanoma and related lesions.