KRAS is a gene that encodes one of the several proteins in the epidermal growth factor receptor (EGFR) signaling pathway that is important in the development and progression of cancer. KRAS can harbor oncogenic mutations that yield a constitutively active protein. KRAS mutations are frequent in low-grade mucinous tumors of appendiceal origin and pseudomyxoma peritonei (43-100%) where mutations commonly occur in codon 12 or 13, with G12D and G12V being the most common. However, appendiceal adenocarcinoma cases with goblet cell features usually lack KRAS mutations. Mutations in the KRAS gene may indicate poor prognosis and drug response with therapies targeted to EGFR in some settings. However, this should be interpreted in conjunction with other laboratory and clinical findings.