Biliary stent–related alterations can be distinguished from adenocarcinoma on bile duct brushings using a limited number of cytologic features

Abstract

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. 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. 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. 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.