F344, Rat Strain

**Semantic type:** Mammal

**Definition:** Most animals older than 2 years exhibit small local areas of nephritis; less than 25% show severe nephritis (Snell 1967). Tumors: Mammary tumors 41% in females and 23% in males, pituitary adenomas 36% in females and 24% in males, testicular interstitial cell tumors 85% in males. Other tumor types less common (Sass et al 1975). Thyroid carcinoma 22% (Lindsey et al 1968). Interstitial cell testicular tumors 65%, mononuclear cell leukemia 24%, subcutaneous fibroadenoma 9% in females. Both sexes have a 5% incidence of nodular hyperplasia of the liver.

**Synonyms:** - F344 - F344 - FISCHER 344 - Fischer 344