title: Clinical and histopathological study of "follicular cholangitis": Sclerosing cholangitis with prominent lymphocytic infiltration masquerading as hilar cholangiocarcinoma.
abstract: OBJECTIVE
  Sclerosing cholangitis which mimic hilar biliary carcinoma have not been fully categorized. In this study, we investigated the clinicopathological features of sclerosing cholangitis of unknown origin, so-called "follicular cholangitis".
  
  
  METHODS
  Patients who had undergone surgery of the proximal bile duct from 1993-2008 on suspicion of proximal bile carcinoma were evaluated. Of these, we investigated the cases compatible with follicular cholangitis. Then, we reviewed the previous reports of follicular cholangitis showing similar clinicopathological findings.
  
  
  RESULTS
  Among 176 patients, two who were diagnosed with benign sclerosing cholangitis of unknown origin shared the common histopathological findings compatible with follicular cholangitis. Histopathological findings showed dense fibrosis with prominent lymph follicles and germinal centers, being appropriate for neither primary sclerosing cholangitis nor immunoglobulin G4-related sclerosing cholangitis. Review of previous published work revealed two other cases diagnosed with follicular cholangitis and showing histopathological findings similar to ours. All these cases were middle-aged patients with no history of autoimmune disease with focal strictures mainly involved in the hilar bile duct, mimicking hilar cholangiocarcinoma.
  
  
  CONCLUSIONS
  Benign sclerosing cholangitis has not been fully categorized, yet. Follicular cholangitis shows unique histopathological features and can be categorized as an independent entity.
authors.affiliation: Division of Digestive Surgery, National Cancer Center Hospital East Division of Clinical Pathology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Fujita
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kojima
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kato
authors.forename: Naoto
authors.initials: N
authors.lastname: Gotohda
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Takahashi
authors.forename: Masaru
authors.initials: M
authors.lastname: Konishi
authors.forename: Taira
authors.initials: T
authors.lastname: Kinoshita