Fine needle aspiration cytology and immunocytochemistry of metastatic melanoma

The cytological and immunological findings of 81 metastatic melanomas are described. Fine needle aspiration was performed from secondary deposits in lymph nodes (38), subcutaneous and soft tissue (36), abdomen (5), lung (1) from 67 patients with histologically verified malignant melanoma. One patient had disease which had spread into the cerebrospinal fluid. Cytomorphologically the cases were classified as classical (47%), carcinoma-like (22%), spindle cell type (14%), lymphoma like (6%), undifferentiated (6%), myxoid type (3%), and clear cell type (2%). All cases were immunologically characterized using antibodies to S-100, vimentin and cytokeratin. All cases were S-100 positive and the majority (96%) reacted with antibodies to vimentin. A weak heterogenous reactivity to cytokeratin antibody was detected in only eight cases. The HMB45 antibody was applied to 20 cases and 16 (80%) of these tumours were positive. In summary, we found that an immunological characterization was necessary to conclusively diagnose over 50% of metastatic melanomas which presented with an equivocal cytological picture.