NZR, Rat Strain

**Semantic type:** Mammal

**Definition:** Tumors (atriocaval epithelial mesotheliomas) of right atrium or inferior vena cava occur in approximately 12-20% of animals of both sexes over 1 year. These tumors are slow growing, but apparently malignant, and closely resemble similar tumors found in humans (Goodall et al 1975). In a later study, most common neoplasms of animal over one year of age: atrioclaval mesotheliomas 12%, lung adenomas 10% (males), pituitary adenomas 23%, mammary tumors 7%, liver tumors 3%, cervical tumors 3% (in females) (Goodall and Doesburg 1981).