PURPOSE: Recently, it was reported that BRAF mutations are frequent in melanoma. 
Previously, we analyzed a large series of paired primary and metastatic 
melanomas for NRAS codon 61 mutations and showed that they arise early and are 
preserved during tumor progression. Here, we have screened the same tumor 
samples for BRAF mutations.
EXPERIMENTAL DESIGN: Primary melanomas (n = 71) and corresponding metastases (n 
= 88) from 71 patients were screened for BRAF exon 11 and exon 15 mutations 
using single-strand conformational polymorphism and nucleotide sequence analysis
RESULTS: BRAF mutations were found in 42 of 71 patients (59%). Thirty-seven 
patients had mutations that lead to a Val599Glu change, whereas mutations 
resulting in Gly468Ser, Val599Arg, Val599Lys, and Lys600Glu changes were 
detected in one patient each. Furthermore, one patient had a 6-bp insertion 
between codons 598 and 599, encoding two threonine residues. In most cases, 
paired primary and metastatic lesions had the same BRAF genotype (i.e., 
mutations present in the primary tumors were preserved in the corresponding 
metastases, and mutations did not arise at the metastatic stage if they were not 
present in the primary lesion). Using laser-capture microdissection, BRAF 
mutations were found in the radial growth phase of the primary lesions. BRAF 
mutations occurred exclusively in tumors that were wild type for NRAS, and in 
total, 89% of the patients analyzed (63 of 71) had mutations in either of these 
two genes.
CONCLUSIONS: The Ras-Raf-mitogen-activated protein kinase/extracellular 
signal-regulated kinase-extracellular signal-regulated kinase signaling pathway 
is activated in the vast majority of melanomas. Activation occurs through either 
NRAS or BRAF mutations, both of which arise early during melanoma pathogenesis 
and are preserved throughout tumor progression.