BRAF Mutation-Positive Folliculotropic Metastatic Melanoma

Primary cutaneous folliculotropic melanoma has been described rarely, and there are even fewer published cases of folliculotropic metastases. We report a 54-year-old man with history of primary cutaneous melanoma of the right posterior shoulder, Breslow depth of 3.4 mm, with one positive sentinel lymph node, negative full axillary dissection, and no extranodal metastases at initial staging. Three years later, he presented with an asymptomatic isolated 2-mm blue-black papule on the scalp and was found to have widespread metastatic melanoma involving lymph nodes, liver, adrenal glands, subcutaneous tissue, skeleton, and lung. Histopathologic examination of the scalp lesion demonstrated a tumor nodule composed of sheets and nests of large round to polygonal cells centered about a hair follicle and within follicular epithelium. BRAF V600E gene mutation was documented in this lesion, and the patient received vemurafenib, with dramatic improvement noted on positron emission tomography scan after 2 months of treatment, soon followed by development of extensive metastases, including to brain. Although BRAF mutations have been found in primary and metastatic melanomas of the skin, and in melanoma metastases of extracutaneous sites, to our knowledge, this is the first case of a BRAF mutation documented in folliculotropic metastatic melanoma.