Michael J. Levy, M.D., a consultant in Gastroenterology and Hepatology at Mayo Clinic's campus in Rochester, Minnesota, discusses clinical utility, optimum specimen collection methods and patient care advantages of using fluorescence in situ hybridization (FISH) testing to detect biliary tract malignancies. Also, Renee M. Root, supervisor of the Mayo Clinic Molecular Anatomic Pathology Laboratory, explains the methodology used when performing the test and differentiating elements of the laboratory's approach.