title: Histopathological and immunohistochemical characterization of spontaneously occurring uterine deciduomas in young adult rats.
abstract: Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.
authors.affiliation: Department of Pathology II, Kansai Medical University, 10-15 Fumizono, Moriguchi, Osaka 570-8506, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yoshizawa
authors.forename: Yuko
authors.initials: Y
authors.lastname: Emoto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Ayako
authors.initials: A
authors.lastname: Kimura
authors.forename: Norihisa
authors.initials: N
authors.lastname: Uehara
authors.forename: Takashi
authors.initials: T
authors.lastname: Yuri
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Shikata
authors.forename: Airo
authors.initials: A
authors.lastname: Tsubura
keywords: decidual reaction; deciduoma; immunohistochemistry; rat; uterus