Benign and malignant mammary tumors induced by DMBA in female Wistar rats.

This study pretends to characterize 7, 12-dimetylbenz[a]anthracene-induced benign and malignant tumors. One hundred and twenty female Wistar rats were randomly allocated to two groups: Control Group and Induction Group; IG animals were given a single dose of DMBA and killed 24 weeks after. Other tumors besides breast tumors were diagnosed, mainly tumors of the salivary glands and ovarian benign epithelial tumors. Incidence of breast disorders was about 60%. Macroscopic mammary tumors varied in dimension from 2 mm to 55 mm. Malignant breast tumors (n = 56) were essentially invasive ductal carcinomas (91.1%), G1 (92.2%), presenting histologic characteristics of good prognosis. Predominant benign breast disorders consisted of glandular (68.6%) and atypical (20%) hyperplasias reproducing histologic types of human breast diseases. Different individual susceptibility to DMBA apparently occurs; while some rats never developed neoplasias, others exhibited several tumors.