NRAS and melanoma: Melanomas may be classified into 3 major classes: 1) sun-shielded melanomas with wild type BRAF and NRAS which have low mutation load but high number of copy gains, 2) sun-exposed melanomas with BRAF or NRAS mutations and 3) sun-exposed melanomas with wild-type BRAF and NRAS, few copy number alterations but high mutation load.