Differential diagnosis of cholangiocarcinoma and IgG4‐related sclerosing cholangitis by fluorescence in situ hybridization using transpapillary forceps biopsy specimens

Background Fluorescence in situ hybridization (FISH) of cytology specimens has been used to diagnose biliary strictures. However, the usefulness of FISH for differentiating between cholangiocarcinoma (CCA) and IgG4‐related sclerosing cholangitis (IgG4‐SC) has not been evaluated in forceps biopsy specimens. Methods We retrospectively reviewed 74 specimens obtained by transpapillary forceps biopsy between 2008 and 2015 from 49 consecutive patients with CCA and 25 with IgG4‐SC. Specimens were considered positive for malignancy by FISH with UroVysion® if at least five cells exhibited polysomy (a gain of two or more in chromosomes 3, 7, or 17). Results A total of 27 (55.1%) patients with CCA, but none of the patients with IgG4‐SC, were positive for malignancy by FISH. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FISH for the diagnosis of CCA were 55.1%, 100%, 100%, 53.2%, and 70.3%, respectively. The complementary use of FISH increased the sensitivity of hematoxylin‐and‐eosin (H&E) staining from 69.4% to 77.6%; the specificity was not reduced when either H&E or FISH was positive. Conclusions The use of FISH in the analysis of forceps biopsy specimens might be one option to differentiate CCA from IgG4‐SC. Highlight With the aim of improving the diagnostic yield, Kato and colleagues evaluated the usefulness of fluorescence in situ hybridization (FISH) using transpapillary forceps biopsy specimens in differentiating between cholangiocarcinoma and IgG4‐related sclerosing cholangitis (IgG4‐SC), which is sometimes challenging. FISH analysis might be a promising option for differentiating cholangiocarcinoma from IgG4‐SC.