Multivariate statistical analysis of bile cytology.

Cytologic features predictive of carcinoma in bile fluid were characterized by a review of 35 cases (22 malignant and 13 benign). Thirty-two cytologic variables were subjected to a stepwise multiple regression model to separate the criteria best suited to the benign versus malignant groups. Six key criteria were selected as useful indicators of malignancy: loss of honeycomb arrangement, enlarged nuclei, loss of polarity, bloody background, flat nuclei and cell-in-cell arrangement. Three or more of these criteria were observed in carcinoma cases more often than they were in noncancer cases (P < .01). By using these criteria, the overall sensitivity of diagnosing carcinoma by bile cytology was 86.4%, and the specificity was 76.9%.