Intra-patient Heterogeneity of BRAF and NRAS Molecular Alterations in Primary Melanoma and Metastases

Mutations in MAPK signalling genes are driver events in melanoma, and have therapeutic relevance in the metastatic and adjuvant setting. This study evaluated the intra-patient heterogeneity of BRAF, NRAS and c-KIT mutational status between 30 primary melanomas and 39 related metastases, using molecular analysis and immunohistochemistry. BRAF mutations were identified in 46.7% of primary melanomas and 48.7% of metastases and NRAS mutations in 20% and 25.6%, respectively. Intra-patient heterogeneity was detected in 13.3% of patients for both BRAF and NRAS genes and was not associated with clinico-pathological characteristics of melanomas or metastases. High consistency was observed between immunostaining and molecular methods for BRAF(V600E) (k = 0.90; p < 0.001) and NRAS(Q61R) (k = 0.87; p < 0.001). These findings demonstrate a relevant intra-patient heterogeneity between primary and metastatic lesions that is independent of clinical variables and methodological approach.