Clinicopathologic characteristics of BRAF V600K mutant malignant melanoma

Background & objectives: BRAF V600K mutation, the second mostcommon mutation in malignant melanoma with a rate of 10-30%, isrelated to worse response to treatment and adverse prognosis. However,data for comparing V600K/V600E groups for the histopathologic andprognostic features are limited.Methods: A total of 23 malignant melanoma cases with BRAFV600E or BRAF V600K mutations detected by pyrosequencingin our department were retrospectively analysed. The associationsbetween the type of BRAF mutations and histopathologic, clinicaland prognostic characteristics were statistically investigated.Results: Of the 23 cases, 7 (30.4%) had V600K and 16 (69.6%)had V600E mutation. Although there was no statistical significancebetween two groups, most of the cases with V600K mutation weremale (85.7%). In BRAF V600K mutant cases, histologic type wasmostly superficial spreading melanoma (85.7%), tumour localizationwas mostly head and neck (57.1%); ulceration and regressionwere slightly higher. In BRAF V600E mutant group, the numberof mitosis (>10/HPF) was higher (81.3%). V600E mutant groupwas generally more advanced (pT4) at the time of diagnosis (75%).In survival analysis, the estimated survival time was shorter inpatients with V600K mutation than those with V600E mutation(17.9 vs 33.2 months).Conclusion: Although it’s a preliminary study and no statisticalsignificance was detected due to the low number of cases, ourresults emphasize that overall survival time is almost half asshort in V600K mutant cases than those with V600E mutation.Considering the prognostic differences, since the double nucleotidechange seen in the V600K mutation(GTG to AAG) includes thesingle nucleotide change seen in the V600E mutation(GTG toGAG), it’s important to be careful in the evaluation to distinguishthese two mutations.