[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. In localized stages, the recommendations remain surgical excision, with almost systematic additional treatment by radiotherapy to reduce the risk of recurrence; there is currently no approved recommendation for adjuvant immunotherapy at this stage. In advanced stages, PD-1/PD-L1 inhibitors as monotherapy have considerably improved the prognosis of patients and are recommended as first-line therapy. However, more than 50 % of patients have primary or secondary failure of these treatments, with no satisfactory option available to date. The use of dual immunotherapy ipilimumab/nivolumab in these refractory patients, or new strategies such as adjuvant or neoadjuvant immunotherapy, are the strategies currently being explored. This article will review the current guidelines on the management of MCC with a summary of the most recent scientific advances.