NRAS and congenital mesoblastic nephroma: In the vast majority of cases, small and medium CMN is more frequently noted to have a BRAF V600E mutation, while large/giant counterparts more frequently harbor NRAS (Q61) mutations.6, 7, 8 CMN are usually benign melanocytic neoplasms, but sometimes it is hard to differentiate CMN from melanoma, especially at an early stage of melanoma.