KRT20 and Merkel cell skin cancer: Since MCCs are frequently misclassified [4], today, immunohistochemistry is performed to confirm the diagnosis: a combination of cytokeratin 20 (CK20), neurofilament (NF), CK7 and thyroid transcription factor-1 (TTF-1) stains are used in order to distinguish MCC from other neoplasms [5].