Frequencies of BRAF and NRAS mutations are different in histological types and sites of origin of cutaneous melanoma: a meta-analysis.

BACKGROUND: There have been conflicting data regarding the prevalence and clinicopathological characteristics of BRAF and NRAS mutations in primary cutaneous melanoma.

OBJECTIVES: To solve this controversy, this study used a meta-analysis to evaluate the frequencies of BRAF and NRAS mutations, and the relationship between these mutations and clinicopathological parameters of cutaneous melanoma.

METHODS: Data from studies published between 1989 and 2010 were combined. The BRAF and NRAS mutations were reported in 36 and 31 studies involving 2521 and 1972 patients, respectively. The effect sizes of outcome parameters were calculated by odds ratios (OR).

RESULTS: BRAF and NRAS mutations were reported in 41% and 18% of cutaneous melanomas, respectively. The mutations were associated with histological subtype and tumour site, but not with age and sex. The BRAF mutation was frequently detected in patients with superficial spreading melanoma (OR=2·021; P<0·001) and in melanomas arising in nonchronic sun-damaged skin (OR=2·043; P=0·001). In contrast, the NRAS mutation was frequently evident in patients with nodular melanoma (OR=1·894; P<0·001) and in melanomas arising in chronic sun-damaged skin (OR=1·887; P=0·018).

CONCLUSIONS: This pooled analysis shows that the incidences of BRAF and NRAS mutations in cutaneous melanomas differ according to histological type and tumour location based on the degree of sun exposure.