title: Spontaneous fibrosarcoma with pleomorphic appearance in an aged brown norway rat.
abstract: An 18-month-old male Brown Norway (BN) rat showed a grayish-white subcutaneous mass in the right cheek. Histologically, the mass was composed of highly pleomorphic cells producing collagen. Immunohistochemical analysis showed that the tumor cells were strongly positive for vimentin and partially positive for Ki-67; however, they were negative for ED-1, ED-2, S-100, cytokeratin, desmin and myoglobin. Ultrastructurally, the cytoplasms of the tumor cells contained well-developed rough endoplasmic reticulum. Thus, the tumor had no characteristic feature other than collagen production and was diagnosed as a fibrosarcoma.
authors.affiliation: Safety Research Laboratories, Dainippon Sumitomo Pharma Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tochitani
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: Yoshiko
authors.initials: Y
authors.lastname: Michimae
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