Eruptive melanocytic nevi secondary to encorafenib for BRAF mutant metastatic colorectal cancer

A 59-year-old woman, undergoing treatment with encorafenib for metastatic BRAF mutated colorectal cancer, developed during the first two months of therapy multiple eruptive nevi and changes in pre-existing nevi. Development of eruptive nevi has increasingly been reported in association with medications, most frequently conventional immunosuppressants and biologics. Some drugs are associated with eruptive nevi through an indirect effect of their mechanism of action, whereas other drugs are directly implicated in melanocyte proliferation. In this regard, BRAF inhibitors have been demonstrated to activate the MAPK pathway, and to promote cellular proliferation and survival, therefore leading to the development of new melanocytic nevi and to an increase in the size and hyperpigmentation of pre-existing nevi. A dermatological assessment and follow-up should be recommended in all patients presenting with eruptive nevi, regardless of the pathogenesis, because a high number of acquired melanocytic nevi may represent an adjunctive risk factor for melanoma.