Mucosal melanomas are a rare subtype of melanoma, arising in mucosal tissues, which have a very poor prognosis due to the lack of effective targeted therapies.,This study aimed to better understand the molecular landscape of these cancers and find potential new therapeutic targets.,Whole-exome sequencing was performed on mucosal melanomas from 19 patients and 135 sun-exposed cutaneous melanomas, with matched peripheral blood samples when available.,Mutational profiles were compared between mucosal subgroups and sun-exposed cutaneous melanomas.,Comparisons of molecular profiles identified 161 genes enriched in mucosal melanoma (P<0.05).,KIT and NF1 were frequently comutated (32%) in the mucosal subgroup, with a significantly higher incidence than that in cutaneous melanoma (4%).,Recurrent SF3B1 R625H/S/C mutations were identified and validated in 7 of 19 (37%) mucosal melanoma patients.,Mutations in the spliceosome pathway were found to be enriched in mucosal melanomas when compared with cutaneous melanomas.,Alternative splicing in four genes were observed in SF3B1-mutant samples compared with the wild-type samples.,This study identified potential new therapeutic targets for mucosal melanoma, including comutation of NF1 and KIT, and recurrent R625 mutations in SF3B1.,This is the first report of SF3B1 R625 mutations in vulvovaginal mucosal melanoma, with the largest whole-exome sequencing project of mucosal melanomas to date.,The results here also indicated that the mutations in SF3B1 lead to alternative splicing in multiple genes.,These findings expand our knowledge of this rare disease.
Since patients diagnosed with BRAF V600E and V600K mutated advanced melanoma show response to treatment with MAP kinase inhibitors, several sensitive methods have been developed to determine the V600 allele status of melanoma patients.,Vemurafenib (Zelboraf) and dabrafenib (Tafinlar) are specific BRAF V600 inhibitors recently approved by the US FDA as single agent treatments for unresectable or metastatic melanoma in patients with the BRAF V600 mutation.,We assessed the new CE THxID™-BRAF diagnostic test, which is also FDA-approved as a companion diagnostic test in the US under a specific reference and compared the results of this assay with both High Resolution Melting (HRM) and Sanger sequencing in 113 melanoma FFPE samples.,Invalid results were observed in 0/113 specimen with HRM, 5/113 (4.4%) with Sanger sequencing, and 1/113 (0.9%) with the THxID™-BRAF test.,Positive percentage agreement (PPA) was 93.5% (95% CI 82.5 - 97.8) for V600E and V600K mutations combined for the THxID™-BRAF test and HRM, and negative percentage agreement (NPA) was 100.0% (95% CI 94.5 - 100.0).,For the THxID™-BRAF test and Sanger, PPA was 100.0% (95% CI 92.1 - 100.0) and NPA 100.0% (95% CI 94.2 - 100.0).,One V600E sample identified by THxID™-BRAF test was detected as wild-type by HRM and uninterpretable by Sanger.,All V600K (n = 3) were detected using the 3 different approaches.,Finally, percent agreement values were not significantly different when using punches (n = 77) vs. slides (n = 36) or depending on samples characteristics such as pigmentation, necrosis, and tumor content.,This study demonstrated the high agreement between the FDA approved THxID™-BRAF assay, HRM, and Sanger sequencing.,It has also highlighted the potential of THxID™-BRAF to be applied to a broader range of sample types than claimed in the current “instructions for use”, an extension that would require the ad hoc validation and approval.