[Merkel cell carcinoma: An update].

Merkel cell carcinoma (MCC) is a rare skin cancer that mainly affects the elderly, and whose incidence is increasing. Although the exact origin of this cancer remains uncertain, research in recent years has revealed that MCC develops through two oncogenesis pathways: virally induced by the Merkel polyomavirus (80% of cases) and induced by mutations linked to ultraviolet rays (20% of cases). MCC is an aggressive cancer, with a high mortality rate and limited therapeutic options in advanced stage.