Five cases (17%) in the present study had a large number of plasma cells intermixed with irregular fibrosis. This sclerosing inflammation is a characteristic histological feature of IgG4-related diseases including AIP, and presumably might be biopsied from the main lesion of the pancreatobiliary system. Indeed, the histological features of lymphoplasmacytic sclerosing pancreatitis are the most important characteristics for diagnosing AIP.19 In addition, all of those cases showed more than 10 IgG4-positive plasma cells per HPF in their bile duct biopsies. In those cases, a definitive diagnosis of AIP or IgG4-SC might be possible from the pathological aspect. The ability to discriminate between IgG4-SC and PSC is

currently an important issue.23 Similar to previous reports, the present study showed that Natural Product Library manufacturer IgG4 immunostaining of the ampullar biopsy is useful for making this distinction. Although a bile duct biopsy is also useful, it should Omipalisib manufacturer be noted that more than 10 IgG4-positive plasma cells might rarely be observed in bile duct biopsies from PSC patients. The pathological features of IgG4-related sclerosing cholangitis and PSC are different.6 IgG4-cholangiopathy inflammation shows a transmural and homogeneous distribution within the bile duct wall. Erosions or intraluminal proliferation of xanthogranulatious tissue are rare.6 IgG4-cholangiopathy

is sometimes associated with an exuberant pseudotumorous inflammatory reaction. In contrast, inflammation is more pronounced on the luminal side with erosions

or ulcerations in patients diagnosed with classical PSC. Before starting the present study, we speculated that these features might be useful for assessing bile duct biopsies. However, it was difficult to examine the distribution of inflammation on biopsied specimens because only luminal tissues were typically biopsied. One of the limitations of the present study was the small number of PSC patients. Therefore, additional studies are necessary to conclude 上海皓元 that bile duct biopsies are useful to discriminate between IgG4-SC and PSC. Another issue was the technical difficulty of bile duct biopsy. Biopsy samples are sometimes small or have artificial degeneration. The quality of the biopsy samples depends considerably on the experience of the endoscopists. One possible interpretation is that the diagnostic rate of pancreatobiliary carcinoma based on a bile duct biopsy is too high in the present study. One explanation for this higher rate is that we have actively carried out this procedure for many patients who were suspected to have this malignancy and have gained technical experience. The present study showed the usefulness of Vater’s ampulla and bile duct biopsies for assessing the number of IgG4-positive plasma cells. Notably, the bile duct biopsy can show not only the number of IgG4-positive cells but also the histological features that are directly related to IgG4-SC or AIP.