Endoscopic bile duct brushing of malignant pancreatic biliary strictures: retrospective study with comparison of conventional smear and ThinPrep techniques.

Endoscopic bile duct brushing (EBDB) is carried out to differentiate benign from malignant biliary strictures in patients who have pancreaticobiliary disease. The sensitivity of this method for the diagnosis of malignancy is relatively low. The aim of this study is to analyze the cytomorphologic features that are helpful in increasing the sensitivity of detecting these lesions on cytologic samples. These features are compared with slides prepared with the ThinPrep technique. The study included 142 patients with bile duct obstruction or pancreatic mass who underwent EBDB and follow-up surgery or biopsy between 1997 to 2000. Twenty-five (18%) of these cases were positive for malignancy in both EBDB and follow-up surgical biopsy; 20 of these cases were used as positive controls (PC). Sixty-one (43%) were negative in both EBDB and follow-up surgical biopsy specimens, and 21 of those cases were used as negative controls (NC). Fifty-six (39%) cases were negative/atypical in EBDB cytology but were suspicious or positive in the surgical or biopsy specimens (false-negative). We identified the cytologic criteria that were helpful in differentiating our positive and negative control groups and applied these criteria to our false-negative group to see whether our sensitivity could be increased, using well-defined cytologic criteria alone. Of the 56 false-negative cases, 9 (16%) were upgraded to suspicious/positive based on the presence of the following features: three-dimensional (3D) micropapillae (95% PC vs 19% NC, P < 0.0001), anisonucleosis (90% PC vs 5% NC, P < 0.0001), high nuclear-to-cytoplasmic (N/C) ratio (95% PC vs 9% NC, P < 0.0001), nuclear contour irregularity (65% PC vs 24% NC, P = 0.0079), and prominent nucleoli (70% PC vs 38% NC, P = 0.0406). Cytomorphologic features which were not helpful in distinguishing positive and negative cases were: single naked nuclei (50% PC vs 28% NC, P = 0.1597), chromatin granularity (50% PC vs 62% NC, P = 0.54), and necrosis (10% PC vs 5% NC, P = 0.5197). Improvement in diagnostic sensitivity for carcinoma of pancreaticobiliary tract in EBDB samples may be achieved by identifying the key malignant cytomorphologic features: 3D micropapillae, anisonucleosis, nuclear contour irregularity, prominent nucleoli, and high N/C ratio. The sensitivity in detecting malignant biliary strictures increased from 31% to 42% based on these criteria in our current study.