BRAF and congenital mesoblastic nephroma: Those described relating to NRAS are loss of the normal allele in NRAS,5 in that case not secondary to a deletion and therefore probably due to postmitotic recombination, and amplification of mutant NRAS. 41 Mutations in BRAF have not been described in melanoma arising in a patient with CMN; however, given the availability and efficacy of BRAF inhibitors it is suggested that both NRAS and BRAF hotspots should be genotyped in cases of melanoma.