Primary mucosal malignant melanoma: an immunohistochemical study of 12 cases with comparison to cutaneous and metastatic melanomas.

Immunohistochemical analysis of 40 formalin-fixed, paraffin-embedded malignant melanomas (12 primary mucosal, 16 primary cutaneous, and 12 metastatic cutaneous) was performed to study the possible differences in immunostaining profiles according to location. The majority of melanomas were reactive with a polyclonal antibody to S100 protein (P-S100; 85%), a monoclonal melanoma-specific antibody (HMB-45; 88%), and a monoclonal antibody to vimentin (90%), and there were no differences in staining profiles for these antibodies by anatomic location. In contrast, while 13 of 16 cutaneous melanomas (81%) and ten of 12 metastatic melanomas (83%) were reactive with a monoclonal antibody to S100 protein (MoAb-079), only five of 12 mucosal tumors (42%) showed positive staining for MoAb-079. Similarly, 14 cutaneous melanomas (88%) and 11 metastatic melanomas (92%) showed positive staining for neuron specific enolase (NSE), while only four mucosal melanomas (33%) were NSE-positive. Of the 40 melanomas, all but two were reactive with either P-S100, MoAb-079, or HMB-45. These findings suggest that MoAb-079 and NSE may be less sensitive markers than P-S100 and HMB-45 for routinely processed mucosal melanomas as compared with cutaneous and metastatic tumors.