DNA Mutational Differences in Cytological Specimens from Pancreatic Cancer and Cholangiocarcinoma

Background/Aims: Preoperative distinction between pancreatic cancer (PC) and extrahepatic cholangiocarcinoma (CC) is desirable due to diverging management options, and to optimize enrollment into neoadjuvant trials. Methods: A single-center retrospective study of patients with PC or CC was undertaken. Four blinded pathologists reviewed all cases and reached a consensus diagnosis (PC or CC). Microdissection-based multiple microsatellite loss analysis and direct sequencing of K-ras oncogene was performed and compared for PC and CC. Results: Of 33 cases studied (17 males; 16 PC, 17 CC; 10 with primary sclerosing cholangitis), a K-ras mutation was present in 14/16 (87.5%) PC and 1/17 (5.9%) CC cases (p<0.001), sensitivity and specificity were 87.5 and 94%, respectively. The mean fractional mutational rate was higher in PC (0.51; 95% CI 0.45-0.58) compared to CC (0.34; 95% CI 0.28-0.39, p<0.001). Conclusions: The presence of a K-ras mutation in cytology specimens distinguishes PC from CC in this study.