Spontaneous lesions in control BALB/C female mice.

The most frequently observed neoplasm in 2376 nontreated control female BALB/cSTCrlfC3H/Nctr mice examined at intervals up to 1001 days was reticulum cell sarcoma. It was also the primary cause of morbidity and death. Other frequently observed neoplasms were uterine polyps, alveolar cell neoplasms, Harderian gland neoplasms and lymphomas. Neoplasms, which had a low incidence, generally occurred in the older animals.