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Background Mutations on KIT and downstream genes of MAPK pathway that overstimulate cellular proliferation have been associated with primary oral and sinonasal melanomas (POSNM), but there is limited information that allows the use of personalized therapy. Thus, the aim of the present study was to determine a possible association between the C‐KIT immunohistochemical expression with the presence of somatic driver mutations in NRAS, BRAF, KIT, MITF and PTEN on POSNM. Methods A retrospective study included 62 tumour samples of an oncological reference centre in Mexico City (17‐year period). Immunohistochemistry stain of C‐KIT was carried out. Genomic DNA was obtained and used to assess hotspot mutations of KIT, NRAS, BRAF, MITF and PTEN through qPCR. Chi‐square, Fisher's exact and the Mann‐Whitney U tests were applied when necessary. The significance was set at P < 0.05. Results Sixty‐two cases were included, 74% were positive for C‐KIT immunoexpression, all exhibited moderate/strong intensity. Ten (16.1%) samples harboured at least one mutation, 6.4% and 6.6% for NRASQ61R and BRAFV600E, respectively, followed by KITK624E (3.2%). No KITL576P, MITF or PTEN mutations were identified. No significant correlation was observed between mutations and immunostaining (rs = −0.057, P = 0.765). Conclusions Regardless of the high immunoexpression of C‐KIT, there was no association with the MAPK mutations among POSNM samples. Thus, C‐KIT immunohistochemistry is not a reliable tool to detect POSNM candidates for biological therapy.

PurposeThe BRAF V600E mutation has been described in melanomas occurring in the Caucasian, European, and Asian populations. However, in the Mexican population, the status and clinical significance of BRAF mutation has not been researched on a large scale.MethodsConsecutive BRAF-tested Mexican patients with metastatic melanoma (n = 127) were analyzed for mutations in exon 15 of the BRAF gene in genomic DNA by real-time polymerase chain reaction technology for amplification and detection. The results were correlated with the clinical-pathologic features and the prognosis of the patients.ResultsThe frequency of somatic mutation V600E within the BRAF gene was 54.6% (43 of 127 patients). Nodular melanoma was the most prevalent subtype in our population, with BRAF mutations in 37.2% (16 of 55 patients). In contrast, superficial spread had a frequency of 18.6% BRAF mutation (eight of 24). Other clinicopathologic features were assessed to correlate with the mutation status.ConclusionThis study searched for the most prevalent BRAF V600E mutation type in melanoma in a heterogeneous population from Mexico. Nodular melanoma was found to be the most prevalent in metastatic presentation and the presence of BRAF V600E mutation, perhaps related to the mixed ancestry; in the north, ancestry is predominantly European and in the south, it is predominantly Asian. The outcomes of the mutation correlations were similar to those found in other populations.

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