Genetically, mucinous adenocarcinomas of the appendix have mutations in exon 2 of the KRAS gene, sometimes in association with mutations in the RNF43 gene or with co-mutations in the GNAS gene, mutations in the GNAS, NRAS, PIK3CA, and AKT1 genes, or mutations in the BRAF gene in association with mutations in the p53 IHC and RNF43 genes, sometimes bearing no mutations at all [10,35,53,54,72,73]. The gene discussed is GNAS; the disease is mucinous adenocarcinoma of the appendix.