BRAF and neoplasm: Compared with BRAF mice (median onset, 24 days), naevus formation in BRAF PREX2 mice was delayed (median onset, 37 days), with no impact on tumor initiation (median, 301 vs. 407 days), or overall survival (median, 375 vs. 466 days; Fig. 1E; Supplementary Fig. S2A).