EUS-FNA Mutational Analysis in Differentiating Autoimmune Pancreatitis and Pancreatic Cancer

Background/Aims: Autoimmune pancreatitis (AIP) may mimic pancreatic cancer (PC). The detection of DNA mutations in endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) material may improve discrimination between AIP and PC and is the context for this study. Methods: In a retrospective study, archived EUS-FNA material from patients with AIP and PC at two centers was analyzed for KRAS mutations and loss-of-heterozygosity analysis involving 18 microsatellite markers. KRAS status and the fractional allelic loss (number of affected microsatellites divided by informative ones) were compared for AIP and PC. Results:Thirty-two patients with 33 samples were studied. There were 16 patients with AIP (17 samples) and 16 patients with PC. DNA amplification failed in 7 samples. Of 25 patients (26 samples), 14 had AIP (7 male, age 57 ± 17 years; mean ± SD) and 11 had PC (7 male, age 65 ± 14 years; mean ± SD). Cytology results for AIP were inflammatory = 3, inconclusive = 10, suspicious for malignancy = 2 and for PC were malignant = 5, suspicious for malignancy = 4 and inconclusive = 2, respectively. KRAS mutation was detected in none of the AIP cases and 10/11 PC cases (91%, Pearson χ2 = 22.16, p < 0.001) or 10/16 PC cases (63%) accounting for PC cases with failed DNA amplification. Mean (±SD) fractional allelic loss for the AIP cases(0.16 ± O.15) was not significantly different from the PC cases (0.26 ± 0.19). Conclusions: A KRAS mutation in EUS/ FNA material from a pancreatic mass is associated with malignancy and may help discriminate from benign conditions Such as AIP.