Merkel cell carcinoma: An update and review: Current and future therapy.

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin associated with a high risk of local recurrence and distant metastases. It most commonly occurs on sun-exposed areas of white patients >65 years of age. The Merkel cell polyomavirus (MCV) is thought to be responsible for malignant transformation in approximately 80% of cases in the northern hemisphere, while ultraviolet radiation-induced DNA damage is implicated in MCV-negative tumors. The overall incidence of MCC is low, with approximately 1600 cases diagnosed annually in the United States. The rate is much higher in patients with lymphoproliferative malignancies, solid organ transplants, and HIV infection. The low overall incidence of this tumor makes it challenging to conduct prospective clinical trials with sufficient power. As a result, most management recommendations are based on case series, retrospective reviews, and expert opinion. The pathogenesis, diagnosis, and staging of MCC was discussed in the first article in this continuing medical education series. This article focuses on current management guidelines and promising new therapies in development. Because of the complexity, aggressive nature, and individuality of each case, MCC is best treated by a multidisciplinary team.