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Side predominance of squamous cell carcinoma: further evidence

lesion size, and the pulmonary nodule disappeared. No adverse events were noted. Nine months after treatment commencement, no lesions have recurred (Fig 2). Clinical appearance of the lesion was consistent with a cutaneous metastasis. Melanoma was favoured, but a primary lesion was not found. Regarding MPNST, half of the cases occur in patients with personal or family history of NF1, neither of which was present in our patient. Histopathologic findings were consistent either with MM or MPNST and immunohistochemical stains were not helpful. Approximately 60% of melanomas have BRAF mutations. A study by Cipriani et al. suggests that BRAF mutations in poorly differentiated spindle cell malignancies may represent melanoma. Serrano et al. looked for mutated BRAF in MPNST with the hypothesis that both melanocytes and Schwann cells are derived from the neural crest. Although they found BRAF mutations in a small subset of MPNST, the percentage was markedly lower than that of MM. Therefore, an activating mutation in BRAF more likely points towards MM. Targeting BRAF mutation with agents like Dabrafenib has been associated with prolonged survival in randomized trials. Its combined use with Trametinib, which blocks MEK, has become an important strategy to overcome BRAF resistance with no increase in adverse events. This case highlights the difficult differential diagnosis between MM and MPNST in cases that present as dedifferentiated spindled amelanotic lesions. Even if melanosomes have not been found, the presence of BRAF mutations supports dedifferentiated melanoma, and targeted therapy may be considered. We encourage clinicians to search for BRAF mutations in poorly differentiated spindled cell tumours because of its diagnostic and therapeutic implications.