New primary melanoma in a patient under triple therapy with vemurafenib, cobimetinib, and atezolizumab for metastatic melanoma.

New primary melanomas (NPMs) in the era of combination treatments for melanoma constitute a challenge for physicians, especially due to the increased incidence of NPMs in patients treated with BRAF inhibitors. We present the unique case of a patient that developed an invasive NPM while under treatment with a combination of vemurafenib, cobimetinib, and atezolizumab. A 39-year-old white male was treated with vemurafenib, cobimetinib, and atezolizumab for a stage IV (T0, N3, M1) BRAF-V600E mutated malignant melanoma in the context of a clinical trial. Eight months from treatment initiation he was diagnosed with an NPM on his back that was found to be BRAF-wild type and neuroblastoma ras mutated, while he was in complete remission. Wide excision of the lesion followed, and the patient was not withdrawn from study treatment. Twenty-two months from treatment initiation, he is still in complete remission. NPMs are a well-known adverse effect of BRAF inhibitors and pose a challenge for the treating physician since these lesions are BRAF-wild type and usually have aggressive biologic behaviour. Invasive NPMs require an aggressive management strategy with clear guidelines to prevent the emergence of advanced or metastatic disease. The emergence of invasive NPMs in patients treated with triple regimens with BRAF/mitogen-activated protein kinase kinase inhibitors and PD1/PDL1 inhibitors is at least unexpected and constitutes a therapeutic stalemate for the physician. Through this case report, we aim to increase awareness about the diagnosis and management of patients with NPM and to express our concerns regarding further management of NPMs in patients under triple combination treatment.