Merkel cell carcinoma: a review

Merkel cell carcinoma (MCC) is a rare aggressive primary cutaneous carcinoma with high mortality and rising incidence. The exact etiology of MCC remains unclear, but it is likely multifactorial with many factors playing a role, among these, ultraviolet radiation, immunosuppression, and recently, Merkel cell polyomavirus. Clinically MCC appears as an asymptomatic, firm, skin colored, sometimes reddish-blue, dome-shaped papule or plaque or subcutaneous nodule typically localized on the head and neck region that has grown rapidly. As its clinical presentation is generally non specific, the diagnosis relies on histological and immunohistochemical findings. Once diagnosis is established, adequate staging requires evaluation of regional and distant metastases. Treatment is based on multidisciplinary management although optimal therapy is controversial, at least in part due to a lack of quality data. Aggressive surgery frequently associated with adjuvant radiotherapy is used to improve the rates of locoregional recurrence and overall survival as well. Future targeted therapies may open new perspectives for the treatment of patients although high-quality, multicentre and randomized studies are needed. In this article, the current knowledge about MCC is reviewed and discussed.