Clinical and pathological characteristics of acute myelogenous leukemia in a female koala with diabetes mellitus.

A female koala presented with hyperglycemia related to diabetes mellitus diagnosed at 9 years and treated with insulin. She presented with nasal hemorrhage, anemia, leukocytosis, and tachypnea at 10 years. A blood smear examination revealed scattered, atypical large myeloid cells and a clinical diagnosis of myelogenous leukemia was made. White blood cell count reached a maximum of 295 × 102/µl, with evidence of severe regenerative anemia and thrombocytopenia. Grossly, systemic lymph node enlargement, fragile liver with hemorrhage, and bloody ascites were observed. Histopathologically, atypical myeloid cells, including myelocytic and metamyelocytic cells, were scattered in the vasculature and surrounding tissues throughout the organs. The patient was infected with a koala retrovirus, which might have caused the myelogenous leukemia.

Poorly differentiated salivary gland carcinoma with prominent squamous metaplasia in a pregnant Wistar Hannover rat.

A subcutaneous pale brown-colored mass was observed macroscopically in the ventral neck of a 16-week-old Wistar rat on day 18 of gestation. The mass was well demarcated from the adjacent tissues with partial invasion into connective tissues. Necrosis and hemorrhage were evident throughout the mass. The mass comprised a diffuse sheet and a nest-like structure of epithelial cells with prominent squamous metaplasia. The neoplastic cells tested immunopositive for keratin, vimentin, glial fibrillary acidic protein and p63. A portion of the neoplastic cells exhibited a similar immunoreaction of prominin-1 to the ductal and acinar cells in normal submandibular and parotid glands. Collectively, the tumor was diagnosed as a poorly differentiated carcinoma derived from epithelial/myoepithelial lineages in the submandibular and/or parotid glands.

Malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure in a female f344 rat.

We report a biphasic malignant mesothelioma in an aged female F344/DuCrlCrlj rat. Macroscopically, multiple pale brown nodules were observed in the abdominal cavity with retention of bloody ascites. Histopathologically, the tumor cells spread over the peritoneum and formed masses on the surface and underlying adipose tissues. The tumor cells dominantly proliferated in a solid, nodular or nest-like pattern with modest amount of fibrillar connective tissues, which contained hyaluronan. The tumor consisted of ovoid, polygonal or spindle-shaped cells that possessed eosinophilic cytoplasms including glycogen; some tumor cells showed a signet-ring-like structure. Multinucleated cells and mitosis were found frequently, and direct invasion to intra-abdominal organs and intravascular metastasis to the liver were observed. Immunohistochemically, keratin and mesothelin were strongly positive in most of tumor cells, while vimentin was mainly positive in spindle-shaped cells. Podoplanin was also positive, particularly in the cell membrane of tumor cells. Electron microscopically, tumor cells showed an intercellular desmosome-like structure, basement membrane and microvillus. We diagnosed the case as a malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure.

Malignant Leydig cell tumor with spindle-shaped cells in a male CD-1 mouse.

Leydig cell tumors with spindle-shaped cells are very rare in humans and animals. We report that an 84-week-old male CD-1 mouse had a malignant Leydig cell tumor characterized by proliferation of oval to spindle-shaped cells with or without fat deposition, and with a storiform pattern. These cells were immunopositive for inhibin and S-100, and negative for the androgen receptor, thereby suggesting that they may have differentiated from Leydig cells. This differentiation from Leydig cells was further confirmed by the immunopositivity of these cells for nestin and alpha-smooth muscle actin, both of which are known to be expressed in the stem/progenitor cells that differentiate into Leydig cells. These findings suggest that the tumor is most probably a malignant spindle-cell-type Leydig cell tumor.