Regional distribution of DMBA-induced mammary tumours in the rat.

Since human mammary cancers have a preference for certain regions of the breast, registration of the topography of DMBA-induced mammary tumours in rats was performed. This revealed that most of the tumours occurred in the upper, or thoracic, mammary glands. While the number of tumours in the two abdominal mammary regions was found to be rather constant, the incidence in the two thoracic regions had a tendency to mutual variations. A regional registration should be made in all experiments dealing with induced mammary tumours.