NKX2-1 and Merkel cell skin cancer: Thereafter, it is absolutely necessary to perform histological and immunohistochemistry analysis to confirm the diagnosis.1,4 If in a clinical evaluation it is difficult to make a diagnosis of MCC, the pathologic analysis is crucial for its identification in the presence of a positive staining for cytokeratin 20, neurofilaments and neuron-specific enolase, and a negative staining for vimentin, thyroid transcription factor 1, and leukocyte common antigen.1,8