Immunocytochemical criteria in the differential diagnosis of malignant melanoma versus carcinoma, lymphoma and sarcoma in fine needle aspirates.

Monoclonal antibodies to keratin, vimentin, leukocyte common antigen (LCA) and S-100 protein have been used in fine needle aspirates of 35 metastatic malignant melanomas, 136 carcinomas, 35 sarcomas and 82 non-Hodgkin's lymphomas in search for immunocytochemical criteria useful in differential diagnosis of melanoma versus carcinoma, non-Hodgkin's lymphoma and sarcoma. All melanomas expressed vimentin and did not express keratin. Six of 14 melanomas contained S-100 protein. All carcinomas were keratin positive. Some were also vimentin positive. All sarcomas expressed vimentin. Synovial sarcomas were also keratin positive. All NHLs were vimentin positive, keratin negative. All NHLs except one expressed also LCA. It is concluded that keratin, vimentin and LCA are useful markers in differential diagnosis of malignant melanoma versus carcinoma and non-Hodgkin's lymphoma in fine needle aspirates when used together with morphologic and clinical data. However, in differential diagnosis of malignant melanoma and sarcoma these markers are of little use.