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Melanoma with BRAF Mutation in Circulating Cell-free DNA despite no Mutation in the Primary Lesion: A Case Report.

Substantial advances have been made recently in the treatment of metastatic melanoma, with the advent of therapies such as BRAF inhibitors (iBRAF), which have been shown to be effective in the treatment of BRAF mutation-positive melanoma (1). The frequency of BRAF mutations is 50–60% in Caucasians and 20–30% in Asian populations (1–3). Mutation is usually determined by Sanger sequencing and high-sensitivity PCR-based methods, such as the Cobas 4800 BRAF Mutation Test (Roche Molecular Diagnostics, Basel, Switzerland), using primary or metastatic lesions. However, the accuracy of these tests is grossly influenced by the quality and quantity of the DNA extracted from the tissues. Thus, BRAF mutation can be missed in cases of contamination, widespread necrosis, or when only small quantities of DNA are available. We describe here a case of advancedstage melanoma with a BRAFV600E mutation. Although the BRAFV600E mutation was not detected in the DNA of the primary lesion, it was detected in circulating cell-free DNA (cfDNA) in peripheral blood. cfDNA includes DNA from apoptotic and necrotic cancer cells, it harbours the genetic alterations present in the tumour (4, 5), and is useful for evaluating tumour features in patients with advanced cancer.