Detection of Polyomavirus in Merkel cell carcinoma by immunohistochemistry: report of three cases

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin, arising from pluripotent precursors of Merkel cells. The tumor most frequently affects head and neck of elderly patients. It increases with sun exposure and after immunosuppression and organ transplantation. Because of a possible viral association, interest in MCC has escalated. A new polyomavirus, Merkel cell polyomavirus (MCPyV), was identified and associated to MCC. In support of this hypothesis, we report three new clinical cases of MCC in which we detected MCPyV by immunohistochemistry and provide an update on current thinking about the MCC.