Merkel cell carcinoma (MCC), or primary neuroendocrine carcinoma of the skin, is an aggressive cutaneous malignancy with 3 times the disease-specific mortality of melanoma (46% vs 15%).1 The annual incidence is approximately 1500 cases in the United States and has been increasing rapidly in recent years, likely partly because of the increasing prevalence of risk factors (eg, aging population, immunosuppression, cumulative ultraviolet light exposure) and improved detection (eg, cytokeratin 20 staining introduced in the 1990s) (Figure 1).2 MCC characteristically presents as a solitary pink or purple nodule (Figure 2) that typically has several of the features summarized in the mnemonic “AEIOU”: Asymptomatic (eg, painless, nonpruritic), Expanding rapidly, Immune suppression, Older than 50 years, and arising on Ultraviolet-exposed, fair skin.3 In 2008, the Merkel cell polyomavirus (MCPyV) was discovered and has been shown to be associated with approximately 80% of MCCs,4 thus joining 6 other viruses now known to be either direct or indirect causes of approximately 50 human malignancies.5
This work was funded by NCATS Grant TL1 TR000422, NIH K24-CA139052, NIH R01-CA162522, the David & Rosalind Bloom Endowment for MCC Research, the Michael Piepkorn Endowment, and the UW MCC Patient Gift Fund. Dr. Moshiri has disclosed that he has no financial interests, arrangements, affiliations, or commercial interests with the manufacturers of any products discussed in this article or their competitors. Dr. Nghiem has disclosed that he is a consultant for EMD Serono, Inc.
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