Kirsten (K)-ras oncogene mutations are present in up to 95% of pancreatic and bile duct adenocarcinomas, with codon 12 K-ras mutations accounting for approximately 75% of this total. The presence of a mutation is nearly 100% specific for carcinoma. The molecular codon 12 K-ras assay has been to be an excellent ancillary test for the tissue diagnosis of pancreas and bile duct carcinoma.

A novel, two step, mutant-enrichment restriction fragment length polymorphism (RFLP) assay to detect codon 12 K-ras mutations from various sources is utilized in the molecular laboratory. Amplicons of various sizes are generated and analyzed after electrophoresis on a 6% polyacrylamide gel. For endoscopic retrograde cholangiopancreatography (ERCP) samples, codon 12 K-ras mutation analysis is a more sensitive method for the diagnosis of pancreatic or bile duct carcinoma than routine cytology alone. The combination of K-ras codon 12 mutation analysis with routine cytology doubles the diagnostic sensitivity compared to routine cytology alone.