title: Cystic cholangioma in the thoracic cavity of a rat.
abstract: A female congenic rat produced by repeated backcrossing of Nihon rats, a model for hereditary renal cell carcinoma, to Brown Norway rats was necropsied at 24 months of age. At necropsy, a white mass about 1 centimeter in size was observed in the thoracic cavity, and the mass partly adhered to the esophagus and the diaphragm. Histologically, the mass was clearly circumscribed by connective tissue, and consisted of neoplastic cuboidal epithelial cells that showed cystic tubular proliferation. Some islands of well-differentiated hepatocytes and some vessels were observed in the mass. Immunohistochemically, the tumor cells were strongly positive for cytokeratin and partly positive for vimentin but were negative for mesothelin and Von Willebrand Factor. The positive rate for Ki-67 was 2.4%. Based on these histological and immunohistochemical evidences, we diagnosed this tumor as a cystic cholangioma that might have arisen from the ectopic hepatic tissue in the thoracic cavity.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Michimae
authors.forename: Kazuo
authors.initials: K
authors.lastname: Okimoto
authors.forename: Kaoru
authors.initials: K
authors.lastname: Toyosawa
authors.forename: Izumi
authors.initials: I
authors.lastname: Matsumoto
authors.forename: Mami
authors.initials: M
authors.lastname: Kouchi
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tochitani
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Koujitani
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Funabashi
authors.forename: Takaki
authors.initials: T
authors.lastname: Seki