Role of fluorescence in situ hybridization in diagnosing cholangiocarcinoma in indeterminate biliary strictures

Background Brush cytology, the conventional method to diagnose cholangiocarcinoma, has been plagued by low diagnostic sensitivity and false-negative results. We aim to study the clinical utility of fluorescence in situ hybridization (FISH) in enhancing identification of malignant biliary strictures. Methods Brush cytologic specimens collected from endoscopic retrograde cholangiopancreatography (ERCP) for biliary strictures in a tertiary hospital in Singapore from March 2013 to July 2015 were examined by FISH technique using UroVysion probe set in this study. Results 30 patients were chosen with 5 patients having multiple FISH done due to indeterminate results. The diagnoses for biliary strictures were 13 (43.3%) cholangiocarcinomas, 7 (23.3%) pancreatic cancers, 7 (23.3%) benign biliary strictures and 3 (10%) primary sclerosing cholangitis. Conventional brush cytology had sensitivity of 53.8% with specificity of 82.4%. FISH had sensitivity of 30.8% with specificity of 100%. When FISH results were interpreted in cases with negative or atypical brush cytology, 2 patients had positive FISH results and cholangiocarcinomas. Based on this pilot study, FISH increased sensitivity of brush cytology in detection of cholangiocarcinoma from 53.8% to 69.2% while preserving specificity of 82.4%. Conclusion Compared with conventional cytology with low sensitivity, FISH may help to increase sensitivity on top of brush cytology while maintaining high specificity.