Nasal adenocarcinoma with myoepithelial component in a CD-1 mouse

Spontaneous malignant myoepithelioma of the maxillary gland in a young adult male BALB/c F1 hybrid mouse

A spontaneous tumor was observed in the maxillary gland of a 12-week-old male BALB/c F1 hybrid mouse. Histopathologically, the tumor invaded both the nasal cavity and maxillary sinus, and ethmoturbinates were destroyed. The majority of the tumor cells had oval nuclei with eosinophilic and vacuolar cytoplasm. Numerous mitotic figures and necrotic foci were also observed throughout the tumor. Immunohistochemically, almost all of the tumor cells were strongly positive for cytokeratin (WSS) and alpha-smooth muscle actin. However, tumor cells were negative for cytokeratin (CAM 5.2), suggesting that these tumor cells originated from myoepithelial cells. The present tumor was diagnosed as a malignant myoepithelioma of the maxillary gland. This is the first report describing spontaneous malignant myoepithelioma in the maxillary gland of a young adult BALB/c F1 hybrid mouse.

Proliferative and nonproliferative lesions of the rat and mouse respiratory tract

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in the respiratory tract of laboratory rats and mice, with color photomicrographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for respiratory tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.