2024 Volume 66 Issue 2 Pages 163-170
A 66-year-old man was referred to our hospital due to obstructive jaundice. Blood examination revealed a high serum IgG4 level of 262 mg/dl. Contrast-enhanced computed tomography revealed a mass in the perihilar bile duct. No pancreatic enlargement was observed. Histopathological examination of the samples from the transpapillary bile duct biopsy under ERCP showed no tumor cells. IgG4 immunostaining was negative. We performed EUS-FNA of the mass in the perihilar bile duct to obtain samples to reach a definitive diagnosis. Histopathological examination of the samples from EUS-FNA showed stromal infiltration of numerous IgG4-positive plasma cells, leading to the diagnosis of IgG4-related sclerosing cholangitis (IgG4-SC). IgG4-SC located in the perihilar bile duct without autoimmune pancreatitis is referred to as isolated proximal-type IgG4-SC. Isolated proximal-type IgG4-SC is sometimes surgically resected because it is difficult to differentiate from perihilar cholangiocarcinoma. In this case report, we describe a case of isolated proximal-type IgG4-SC diagnosed using EUS-FNA.
