Epidemiology and genetics (including high risk patients, polyomavirus, prognostic factors)

Merkel cell carcinoma (MCC) is a rare, highly aggressive form of skin cancer that has a strong propensity toward local recurrence, regional nodal metastasis, distant metastasis, and high mortality rates. MCC usually affects elderly white persons and has been described with many different names, given the uncertainty of the cell of origin. The most commonly used names include trabecular carcinoma of the skin, cutaneous neuroendocrine carcinoma, and Merkel cell carcinoma. The name Merkel cell carcinoma was suggested in 1980 and is the most common name used today. The incidence of MCC in the United States is estimated at 0.6 per 100,000 person-years. Because of the rarity of this form of skin cancer, studies have been limited in the past regarding MCC etiologic characteristics, risk factors, prevention strategies, and therapeutic approach. However, population-based data have been accessed recently, mainly from cancer registries, allowing for more detailed information to come to light on the demographic characteristics of primary MCC in the general population. Recently, discoveries of factors that could contribute to the development of MCC have been made, including the identification of the Merkel cell polyomavirus and genetic mutations.