Vemurafenib-associated neutrophilic panniculitis in a patient with metastatic amelanotic melanoma presenting as cancer of unknown primary origin

The treatment of metastatic melanoma is challenging. BRAF gene mutation is found in 40–60% of melanoma cases, the most common being the V600E mutation. Vemurafenib was approved by the Food and Drug Administration in 2011 as target therapy for the treatment with BRAF V600 mutation-positive metastatic melanoma. We report a case of metastatic amelanotic melanoma with unknown primary cancer as the initial presentation. The patient presented with neutrophilic septal panniculitis 1 week after vemurafenib treatment, which is a rare cutaneous toxicity of BRAF inhibitor. We also review the current literature on management of BRAF inhibitor-related adverse skin effects.