Alpha2u-globulin is an adult male rat-specific protein that accumulates spontaneously or inductively in the renal proximal tubular epithelium and forms microscopically observable deposits, which are generally referred to as “hyaline droplets,” whereas a specific type of deposits is referred to as “eosinophilic bodies” by Japanese toxicologic pathologists. We compared hyaline droplets and eosinophilic bodies using special stains including immunostaining for α2u-globulin and lysosome-associated membrane protein in spontaneously occurring and d-limonene-induced cases. Eosinophilic bodies appeared simultaneously and increased in parallel with the hyaline droplets in the induced case. In both of the spontaneous and induced cases, hyaline droplets and eosinophilic bodies were associated with α2u-globulin and lysosomes, although there were differences in the forms and staining properties that probably reflected the purity or density of α2u-globulin. According to the results, it is not necessary for eosinophilic bodies to be strictly distinguished from hyaline droplets, and it is reasonable to identify eosinophilic bodies as hyaline droplets in α2u-globulin nephropathy in routine toxicity studies, as they have been recognized to be a sequence of changes associated with accumulation of α2u-globulin.

A tumor was observed in the left mandible of a 3-year-old male Shih-Tzu dog. Histopathology revealed neoplastic alveolar proliferation of round cells, sarcomatoid proliferation of round to spindle-shaped cells and an existing parotid gland tissue around the tumor. A cancellous bone framework was also seen throughout the tumor. The tumor cells in the sarcomatoid area were positive and weakly positive for vimentin and cytokeratin, respectively, demonstrating their myoepithelial character. We diagnosed this tumor as a malignant mixed tumor of the salivary glands, because of the location of the tumor, its invasiveness into the surrounding tissue and the identification of both epithelial and myoepithelial tumor cells.

Congenital vitelline duct anomalies other than Meckel’s diverticulum are rare in animals. A cyst of approximately 8 mm in diameter was observed on the antimesenteric surface of the ileal serosa in a 10-week-old female Crl:CD(SD) rat. Microscopically, the cyst closely resembled the ileum, but it did not communicate with the ileal lumen. We diagnosed this case as a vitelline cyst derived from the vitelline duct based on the location where it developed and its histological behavior. In rats, only Meckel’s diverticulum has been reported with a congenital anomaly of the vitelline duct, and no other spontaneous anomalies including a vitelline cyst have been reported. This case may be the first report concerning a vitelline cyst in the rat ileum.

Abstract:In a study to collect background data using c-Ha-ras transgenic mice (rasH2 mice), epithelial proliferative lesions were observed in the nasal cavities of the animals with or without administration of a single intraperitoneal dose of N-methyl-N-nitrosourea (MNU). These proliferative lesions occurred most frequently in the ventral meatus of the incisive papilla (nasal cavity in the specimen). Most of the proliferative lesions were a polypoid or papillary form consisting mainly of an epithelium resembling a squamous epithelium. In addition, administration of MNU tended to increase the incidence of proliferative lesions. Therefore, in carcinogenicity studies using rasH2 mice, we may come across epithelial proliferative lesions in the nasal cavity. (J Toxicol Pathol 2008; 21: 193-197)