A case of follicular cholangitis mimicking hilar cholangiocarcinoma.

Follicular cholangitis is a sclerosing cholangitis with hilar biliary stricture that must be differentiated from both immunoglobulin G4-related sclerosing cholangitis and primary sclerosing cholangitis. This disorder is extremely rare and difficult to distinguish from hilar biliary cholangiocarcinoma. We report here a case of a Japanese female patient in her 60s with this disease. The patient visited a family doctor for itching and general fatigue. Blood examination showed elevated hepatobiliary enzyme levels. Various imaging studies showed dilation of the bilateral intrahepatic bile duct and wide stenosis from the proximal bile duct to the right and left hepatic duct. They also showed the enlargement of multiple lymph nodes in the hepatoduodenal ligament, periaorta, and mesocolon. Based on endoscopic retrograde cholangiopancreatography-directed brush cytology, we diagnosed this patient with hilar cholangiocarcinoma and performed left trisegmentectomy of the liver. The pathology results showed that the wall from the bilateral hepatic duct to the proximal bile duct had thickened irregularly with dense fibrosis and a marked formation of lymph follicles. The mucosal epithelia did not have malignant findings. The diagnosis was follicular cholangitis. This case indicates that follicular cholangitis should be considered as a differential diagnosis of hilar biliary stricture.