title: Mixed Type of Malignant Mesothelioma in an Aged Male ICR Mouse.
abstract: Multiple whitish nodules in the thoracic cavity at the site of the thymus were observed in a 101-week-old male ICR mouse. In a histopathological examination, the neoplastic cells were predominantly fusiform in shape and proliferated in sarcomatoid growth patterns. Some neoplastic cells showed epithelial growth patterns, such as the ductal structures. Mitotic figures were frequently seen, and small necrotic foci and invasion to adjacent thoracic organs were noted. In Alcian blue staining, bluish materials were observed between fusiform-shaped cells and in some of the lumens of the ductal structures. In immunohistochemistry, both fusiform-shaped and ductal structure-forming cells were positive for vimentin and weakly positive to positive for cytokeratin. Based on the aforementioned findings, the thoracic nodules were diagnosed as a mixed type of malignant mesothelioma. This case was thought to be rare because of the very low occurrence of spontaneous mesothelioma in mice.
authors.affiliation: Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., 717 Horikoshi, Fukuroi,Shizuoka 437-0065, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirai
authors.forename: Takanori
authors.initials: T
authors.lastname: Maejima
authors.forename: Tomoe
authors.initials: T
authors.lastname: Tanimoto
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Kumagai
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Makino
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Kai
authors.forename: Munehiro
authors.initials: M
authors.lastname: Teranishi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sanbuissho