While for the first half of the discrepant cases, one could infer that selection of BRAF/NRAS mutant alleles may occur during tumor progression, for the second series, one could speculate that primary melanoma may be heterogeneous with different tumor cell types (one mainly represented and the others less represented, which may be able to however give origin to metastatic subclones in a subset of cases). The gene discussed is NRAS; the disease is neoplasm.