Genesis of breast cancer is in the premenopause

In Britain and other high-risk countries, about a third of patients with breast cancer are premenopausal at diagnosis. In the remainder, tumour initiation might have occurred in the premenopause, even though the clinical presentation was late in life. This possibility has important implications for breast cancer prevention and screening. The relations between the patient's age and tumour kinetics, prognosis, oestrogen receptors, and environmental X-ray carcinogenesis were studied, together with the age-related protection afforded by pregnancy. The findings support the hypothesis that breast cancer is initiated in the premenopause.