Merkel Cell Carcinoma

Abstract

Merkel cell carcinoma (MCC) is a rare, primary, highly malignant cutaneous neoplasm with epithelial and neuroendocrine differentiations that predominantly occurs in fair-skinned, elderly Caucasians and immunocompromised patients. It was first described in 1972 by Cyril Toker as a trabecular carcinoma. The true origin is unknown. Until recently, Merkel cells were believed to be at the origin of MCC, but recent studies show that MCC are more likely to arise from epidermal stem cells. The exact etiology is not known, but is postulated to relate to sunlight, immunosuppression, and infection by a Merkel cell polyoma virus. In fact, the frequent detection of the virus in the tumor (70–90 %), its monoclonal integration in the tumor cells, and the expression of viral oncogenes highly suggest that the virus is causally linked to the pathogenesis of MCC cases.