Immunohistochemical diagnosis of sinonasal melanoma, carcinoma, and neuroblastoma with monoclonal antibodies HMB-45 and anti-synaptophysin.

The efficacy of two new monoclonal antibodies with cell lineage-restricted reactivity (HMB-45 [melanocytes] and anti-synaptophysin [neuroepithelial cells]) was compared with that of "traditional" antibody panels in the delineation of malignant melanoma (MM) of the sinonasal region, nasopharyngeal carcinoma (NPC), and olfactory neuroblastoma (ONBL). HMB-45 recognized all of eight melanomas and stained one of five neuroblastomas, but failed to label any of 12 cases of NPC. All examples of ONBL were stained by anti-synaptophysin; other tumors were nonreactive with this reagent. A panel of antibodies to cytokeratin, vimentin, epithelial membrane antigen, and S100 protein was also effective in discriminating between MM, NPC and ONBL. These results suggest that HMB-45 and anti-synaptophysin are comparable in utility to more extended antibody panels in the diagnosis of sinonasal malignancies, but only if used in combination with one another.