title: Extraskeletal osteosarcoma with cystic appearance in an aged Sprague-Dawley rat.
abstract: Extraskeletal osteosarcoma, arising spontaneously from the subcutis of the left abdomen and having a cystic appearance, was found in an untreated male Sprague-Dawley rat during a carcinogenicity study. At 76 weeks of age, the tumor mass had grown to 50 x 110 x 140 mm, and the animal exhibited severe anemia related to the complication of ulceration with hemorrhage. The tumor displayed irregular ossification at the walls of a cyst-like space filled with much yellowish fluid and necrotic cellular debris. Histopathologically, the tumor consisted of sheets of large, plump osteoblast-like cells, which produced broad irregular trabeculae of osteoid and calcified osseous tissue. Since extraskeletal osteosarcoma with a cystic appearance, has not been reported in animals, except for the telangiectatic type, our case shows an extremely rare type.
authors.affiliation: Toxicologic Pathology, Drug Safety Research Laboratories, Astellas Pharma Inc., Kashima 2-1-6, Yodogawa, Osaka, Japan. katsuhiko.yoshizawa@jp.astellas.com
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yoshizawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Oishi
authors.forename: Abraham
authors.initials: A
authors.lastname: Nyska
mesh_terms: D000008:Abdominal Neoplasms / Q000473:pathology*; D000740:Anemia / Q000209:etiology; D000818:Animals; D006470:Hemorrhage / Q000209:etiology; D008297:Male; D009336:Necrosis; D009999:Ossification, Heterotopic / Q000473:pathology; D012516:Osteosarcoma / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley