Risk factors in breast cancer.

Risk factors are identified in less than 25 per cent of women who develop invasive breast cancer. The risk factors include a family history of breast cancer in a first degree family relative, late menopause, nulliparity, a first full term pregnancy after the age of 35 years, increasing age, P2 and DY mammographic parenchymal patterns, increasing dosage of non contraceptive oestrogens, mammary dysplasia associated with epithelial proliferation, a previous invasive breast carcinoma and carcinoma in situ.