prediagnosis of breast cancer

The causes of breast cancer are not fully understood. Ageing, genetic factors and environmental influences all appear to play a part,22 although the effects of some of these risk factors may be different for younger and older women.23,24 For younger women, a strong family history of breast cancer is one of the most important risk factors.23 However, most young women who develop breast cancer do not have a family history of the disease.

Other factors that may be associated with increased breast cancer risk for younger women include: a history of proliferative benign breast disease; nulliparity, low parity, or late age at first full-term pregnancy; and short duration of breastfeeding or never having lactated.24 Current or recent use of combined oral contraceptives is associated with a slightly increased risk of breast cancer, but there is no evidence of excess breast cancer risk 10 or more years after cessation of oral contraceptive use.25 A link between induced abortion and breast cancer risk has been hypothesised, but the results of a large, populationbased study suggest that induced abortions have no overall effect on the risk of breast cancer, regardless of age.26