The Development of Malignant Melanoma Concurrent to Encorafenib and Cetuximab Therapy for Gastrointestinal Cancer With Neuroendocrine Features.

BRAF inhibitors, among other targeted therapies, have transformed the treatment of many cancers in recent years. While cutaneous malignancies are a known adverse effect of BRAF inhibitors, the following case description highlights the importance of regularly monitoring patients on these therapies for new or changing skin lesions. A female in her 70s presented to the dermatology clinic with the sudden development of several new, dark nevi one month after the initiation of encorafenib with cetuximab for neuroendocrine carcinoma. Biopsy results were positive for a superficial spreading melanoma and a separate lesion demonstrating severe histologic atypia. Procedural dermatology performed a complete excision of both lesions.