The diagnosis of MCC of the skin by FNA can be made by applying cytologic features in addition to ancillary studies and clinical information . The malignant cells in MCC are characteristically positive for cytokeratin (CK) 20 (punctuate, globular/perinuclear pattern of staining), neuroendocrinethe markers like synaptophysin and chromogranin (focal positivity), and negative for thyroid transcription factor (TTF-1, pulmonary or thyroid origin excluded) and CD45 (lymphoma excluded) . The MCC cells are also positive for CAM5.2 and CD56 (neuroendocrine marker). ICC results in MCC are universally positive for Ck, which show a paranuclear "dot-like" pattern; neurone-specific enolase, epithelial membrane antigen, and S-100 protein are positive in varying degrees, but leucocyte common antigen is universally negative . Skoog et al  observed a peculiar dot-like cytokeratin positivity and diffuse NSE positivity in four MCC diagnosed by FNA. A weak positivity for S-100 was observed. Das et al  described a metastatic MCC, in which immunocytochemical stainings on FNA smears revealed focal button-like Ck positivity, diffuse positive reaction for chromogranin, and negative reaction for LCA (Figure 4 C and D).
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