The following risk factors have been identified.
- Female gender: About 11 percent of women develop breast cancer.
- More advanced age: 77 percent of women diagnosed with breast cancer are over 50.
- Having one first-degree relative (mother, sister or daughter) with breast cancer doubles risk; having two increases risk five-fold.
- Approximately 10 percent of breast cancers are the result of inherited mutations (changes) of the genes BRCA1 and BRCA2, which make proteins that help prevent cancerous growth.
- Risk increases significantly if you have had cancer of the breast, ovaries, uterus or colon. Cancer in one breast means a one percent chance per year of developing cancer in the other breast.
- When a biopsy indicates abnormal cells that aren't yet cancerous (atypical hyperplasia), there's moderately increased risk of developing cancer in future. Atypical hyperplasia is a benign condition associated with abnormal growth of cells. A young patient with this diagnosis is very likely to develop a cancer.
- Risk increases slightly if you have had a benign breast lump.
- Obesity (being overweight) is a possible risk, especially after menopause.
- A diet high in saturated animal fats may increase risk.
- Compared to non-drinkers, women who consume one alcoholic drink daily may have a small increase in risk; those who have two to five drinks daily have about twice the risk.
- Exposure to oestrogen increases risk. Oestrogen stimulates cell division: the more cells divide, the more likely it is that some may become cancerous.
- Women with early onset of menstruation, late menopause, a menstrual cycle shorter or longer than average, no pregnancies or first pregnancy after 30, have slightly higher risk.
- Oral contraceptives may slightly increase risk. Women who stopped using oral contraceptives over 10 years ago do not appear to have increased risk.
- More than eight years of hormone replacement therapy (HRT) increases the risk. Risk returns to that of the general population within five years of stopping HRT.
- Recent research suggests that smoking may increase the risk.
As more women have mammograms, and with improved detection and treatment options, rates of new cases of breast cancer have increased. The rate of death from all types of breast cancer hasn't increased, however, as treatment is getting more effective. Breast cancer is still the most common cancer in women. The disease is more common in older women, urban areas, higher socio-economic groups, unmarried women and Jewish women. Caucasians (especially of northern European descent) are slightly more at risk. Asian and Hispanic women have lower risk. Incidence in black women, specifically those of African descent, is increasing.
Signs and symptoms
Any woman should seek advice if she notices any change in her breast. Later symptoms may include:
- Breast lumps: usually painless, but some cause a prickly sensation.
- Change in nipple appearance: the shape or the skin may change.
- Unusual nipple discharge: especially stained with blood.
- Change in the skin of the breast. A lump or swelling under the arm.
- Breast swelling. Vague discomfort in the breast.
- Breast pain or tenderness. Change in breast contour, texture or temperature.