Some known risk factors for developing breast cancer include:

• Getting older.
• Having a family history of breast cancer
• Having previously been diagnosed with breast cancer or DCIS.

Other risk factors that seem to slightly increase a woman's risk of developing breast cancer include:

• Starting menstruation, or 'periods', at a relatively early age (before 12 years); and starting menopause, or 'change of life', at a relatively late age (after 55 years).
• Not breast feeding - the more months spent breast feeding, the lower risk of developing breast cancer.

• Not having children, or having a first child after 35 years of age.
• Taking combined Hormone Replacement Therapy (HRT) after menopause, especially when taken for 5 years or longer.
• Putting on a lot of weight in adulthood, especially after menopause.
• Drinking alcohol (more than 2 standard drinks a day).
• Taking the oral contraceptive pill - this appears to only increase the risk during the period of taking the pill; the risk goes back down after you stop taking it.
• Having previously been diagnosed with lobular carcinoma in situ (LCIS) or atypical hyperplasia (AH).