Risk of malignancy in indeterminate biliary tract strictures: Retrospective cohort study.

Background: Indeterminate biliary strictures, that is, a stricture with benign brush cytology but without clear etiology in clinical or radiological assessment, pose a challenge for clinicians. This study aimed to assess the incidence and risk factors for malignant disease in patients with indeterminate biliary strictures.

Methods: This is a single-center retrospective study of patients with indeterminate biliary stricture undergoing first endoscopic retrograde cholangiopancreatography (ERCP) and biliary brushing between March 2011 and March 2020. The study included patients with atypical cytology in the first ERCP biliary brushing samples. Main exclusion criteria were primary sclerosing cholangitis, apparent malignancy or tumor in imaging studies, postoperative strictures, chronic pancreatitis, biliary tract stone, and no ≥12-month follow-up or a final pathological diagnosis.

Results: A total of 2279 patients underwent first ERCP procedure because of a biliary tract stricture during the study period, of which 51 patients (2.2%) had an indeterminate biliary stricture and were included. A total of 30 patients (58.8%) had final diagnosis of malignant disease. The patients with final diagnosis of malignant disease were mostly men (n = 19, 63.3%), had jaundice (n = 25, 86.2%), and had significantly higher bilirubin and CA19-9 values than those with benign disease. A total of 25 patients were operated on, of which 21 patients (84%) had malignant disease. Twenty-six patients were followed up only, of whom nine patients (34.6%) had a malignant disease.

Conclusion: Indeterminate biliary strictures are uncommon, but two-thirds of the initially indeterminate biliary strictures are malignant. The presence of clinical jaundice and elevated bilirubin and CA19-9 values are associated with increased risk of malignancy.