Accurate clinical evaluation of biliary strictures remains highly challenging. The purpose of this prospective study was to compare the diagnostic utility of standard FISH testing of cells and/or mutation profiling of free DNA, when used in combination with routine cytology, to detect malignancy. Histologic diagnosis (histology from biopsy or cytology for fine-needle aspiration) in conjunction with clinical and/or imaging follow-up was used as the gold standard for diagnosis of malignancy (n=101).

Cytology provided 26% sensitivity and 100% specificity for malignancy. Using either FISH or mutation profiling in combination with cytology increased sensitivity to 44% and 56%, respectively. The combination of all 3 tests (cytology, FISH, and mutation profiling) had the highest sensitivity for malignancy (66%). There was no difference in the specificity of cytology, FISH, or MP testing when examined alone or in combination. Mutation profiling improved the diagnostic yield of each procedure from 22% to 100%; FISH improved the yield to 90%. Mutation profiling detected 21 malignancies beyond those identified by cytology; FISH detected an additional 13. The combination of FISH and mutation profiling detected an additional 28 malignancies.

Both mutation profiling and FISH are complementary molecular tests that can significantly increase detection of biliary malignancies when used in combination with routine cytology of standard biliary brush specimens.