title: Spontaneous extraskeletal osteosarcoma with various histological growth patterns in the abdominal wall of an ICR mouse.
abstract: Extraskeletal osteosarcoma is extremely rare in mice. This case report demonstrates a spontaneous murine extraskeletal osteosarcoma that exhibited various histological growth patterns in an ICR mouse. At necropsy, the tumor mass was located in the abdominal wall and was 45 × 30 × 25 mm in size. Histopathologically, the tumor showed the following four growth patterns: a solid pattern of polygonal cells embedded in an osteoid eosinophilic matrix with calcification, an irregular sheet pattern of short spindle cells accompanying some eosinophilic multinucleated cells, a fascicular pattern of spindle cells and a cystic pattern lined by short spindle cells. Immunohistochemically, most of the tumor cells were positive for vimentin, proliferating cell nuclear antigen and osterix. The multinucleated cells mentioned above were desmin positive and were regarded as regenerative striated muscles but not tumor cells. Since no clear continuity with normal bone tissues was observed, the tumor was diagnosed as an "extraskeletal osteosarcoma."
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ito
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Katoh
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Shimada
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Ohnuma-Koyama
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Kuwahara
authors.affiliation: The Institute of Environmental Toxicology, 4321 Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Harada
keywords: abdominal wall; extraskeletal osteosarcoma; mouse; osterix; spontaneous tumor