POLYMERASE CHAIN REACTION-BASEDK-RAS MUTATION DETECTION OF PANCREATICADENOCARCINOMA IN ROUTINE CYTOLOGY SMEARS

The cytologic diagnosis of pancreatic carcinoma is notoriously difficu lt, particularly in distinguishing benign atypia from web-differentiat ed adenocarcinoma. Mutation of codon 12 in the K-ras oncogene is frequ ently found with pancreatic cancers. Detection by polymerase chain rea ction (PCR) followed by restriction endonuclease digestion can provide a powerful tool to improve and confirm diagnosis. The authors examine d the utility of PCR-based detection in the diagnosis of pancreatic ca rcinoma using routinely obtained cytology smears that could be collect ed at most hospitals. Pancreatic cytology smears were collected retros pectively from 60 patients. DNA was extracted from the slides and ampl ified by PCR using mismatched primers that generated a Bst-N1 recognit ion site with the wild type codon IZ but not with the mutant allele. R esults were compared with clinical follow-up. K-ras codon 12 mutations were observed in 44 of 46 (95.7%) cases of pancreatic cancer, but not in 12 benign cases nor in 2 cases of islet cell tumor. The amplificat ion and digestion steps proved robust and sensitive, capable of detect ing mutant K-ras alleles from cytology smears that contained only smal l foci of suspicious cells. Our results indicate that K-ras mutation a nalysis can be done reliably within 1 to 2 days from routine cytology slides without special handling, increasing the sensitivity of diagnos is in ambiguous cases while maintaining cost-effective and relatively noninvasive sampling strategy.