In the 11 extramedullary plasmacytomas, mutations were detected in the NRAS gene in 27% of cases (n = 3) and in the BRAF gene in 18% (n = 2), suggesting a tendency for KRAS mutations to be more frequent in bone lesions, while NRAS mutations were more common in extramedullary sites. This evidence concerns the gene NRAS and plasmacytoma.