RESUMO
A female congenic rat produced by repeated backcrossing of Nihon rats, a model for hereditary renal cell carcinoma, to Brown Norway rats was necropsied at 24 months of age. At necropsy, a white mass about 1 centimeter in size was observed in the thoracic cavity, and the mass partly adhered to the esophagus and the diaphragm. Histologically, the mass was clearly circumscribed by connective tissue, and consisted of neoplastic cuboidal epithelial cells that showed cystic tubular proliferation. Some islands of well-differentiated hepatocytes and some vessels were observed in the mass. Immunohistochemically, the tumor cells were strongly positive for cytokeratin and partly positive for vimentin but were negative for mesothelin and Von Willebrand Factor. The positive rate for Ki-67 was 2.4%. Based on these histological and immunohistochemical evidences, we diagnosed this tumor as a cystic cholangioma that might have arisen from the ectopic hepatic tissue in the thoracic cavity.
RESUMO
A male ferret, which was purchased from abroad at 9 months of age, had shown significant weight loss starting at 13 months of age. The ferret subsequently showed decreasing motor activity and recumbency and was euthanized at 14 months of age. At necropsy, a white, quail egg-sized mass was found in the mesentery. Histopathologically, multifocal granulomas consisting of necrotic foci, macrophages, fibroblasts and plentiful fibrous connective tissues were observed in the mesenteric mass. Surrounding the granulomas, inflammatory cell infiltration consisting of neutrophils, lymphocytes and plasmacytes was observed diffusely and significantly. Immunohistochemistry revealed small numbers of macrophages around necrotic foci that were positively stained for anti-mouse feline coronavirus. Electron microscopically, the cytoplasm of the macrophages contained viral particles, which were identified as coronavirus. The histopathological features in this ferret were similar to those in cats with feline infectious peritonitis (FIP). This was the first case in ferrets in Japan.
RESUMO
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.
RESUMO
Fibromatosis-type fibromas were found to develop at abdominal surgical sites in 4 heterozygous Nihon rats, a model for the human Birt-Hogg-Dubé syndrome. In all 4 rats, solitary and firm nodules were located within the lateral abdominal musculature involving the full thickness of the abdominal wall at the sites of laparotomy. Histologically, the nodules consisted of well-differentiated fibroblastic spindle-shaped cells. These cells were surrounded by large amounts of collagen fibers, and appeared to infiltrate within the abdominal musculature. A portion of the spindle-shaped cells showed features of myofibroblasts. These characteristics are consistent with desmoid tumors in human. Although the etiology of desmoid tumors in human remains unclear, they are known to occur in association with hormonal factors, surgical trauma, and familial adenomatous polyposis. In animals, they have been reported in dogs, cats, horses, and genetically modified mouse models for human familial adenomatous polyposis. The development of the tumors in the Nihon rats was apparently associated with surgical incisions. Genetic factor should be involved in the occurrence of the tumor, since it was found only in the Nihon rats among many rats. Our present data suggest that Bhd gene mutation is not likely to be a candidate.
Assuntos
Fibroma/etiologia , Fibroma/genética , Fibroma/ultraestrutura , Laparotomia/efeitos adversos , Proteínas/genética , Animais , Modelos Animais de Doenças , Mutação , Ratos , Ratos MutantesRESUMO
An 8-year and 6-month-old female Maltese dog showed a stoop with rigidity of her cervix and back. Neurologic examination showed loss of proprioception, and deficiency of pain response. Postmortem examination revealed the neoplastic mass replacing the central area in the cervical spinal cord at the level from 4th to 5th segments. Histologically, the mass was composed of neoplastic ependymal cells. The neoplastic cells showed marked atypism, and occasionally formed ependymal rosettes. Based on the morphologic features, the tumor was diagnosed as anaplastic ependymoma. Immunohistochemistry showed that the neoplastic cells were negative for glial fibrillary acid protein, and slightly positive for vimentin and cytokeratin.