ABSTRACT
INTRODUCTION: Although it is widely accepted that cytologic alterations secondary to a biliary stent can be difficult to distinguish from adenocarcinoma in pancreatobiliary exfoliative cytology, no systematic study has been undertaken to identify the cytologic features that best distinguish these entities. MATERIALS AND METHODS: A training set of 29 bile duct brushings (14 with biliary stents, originally classified as atypical or suspicious, with >6 months of benign clinical follow-up; and 15 diagnosed as adenocarcinoma with histologic confirmation) was evaluated for the following: nuclear enlargement, nuclear contour, nuclear overlap, chromatin distribution, nuclear-cytoplasmic ratio, anisonucleosis, macronucleoli, mitoses, acute inflammation, disorganization, necrosis, cell borders, single atypical cells, and 2 distinct cell populations. A distinct validation set of 31 equivocal stented brushings-13 later diagnosed with carcinoma and 18 with ≥6 months of benign follow-up-were similarly evaluated. Cases were categorized as benign or malignant using a scoring algorithm based on statistically significant features. RESULTS: Five features achieved statistical significance: atypical single cells (P = 0.0001), 2 distinct cell populations (P = 0.0007), and anisonucleosis (P = 0.0422) favored malignancy; distinct cell borders (P = 0.0018) and acute inflammation (P = 0.0035) favored benign. The algorithm correctly classified 12 of 14 benign and 15 of 15 malignant cases in the training set and 16 of 18 benign and 7 of 13 malignant cases in the validation set. CONCLUSIONS: Most bile duct brushings from patients with biliary stents could be definitively and correctly classified as either benign or malignant using 5 morphologic features: single atypical cells, binary cell population, anisonucleosis, distinct cell borders, and acute inflammation.
