Risk factors:
A risk factor is anything that makes it more likely you'll get a particular disease. But having one or even several risk factors doesn't necessarily mean you'll develop cancer-most women with breast cancer have no known risk factors other than simply being women.

In fact, being female is the single greatest risk factor for breast cancer:

Other factors that may make you more susceptible to breast cancer include:

• Age. Your chances of developing breast cancer increase with age. Close to 80 per cent of breast cancers occur in women older than age 50. in your 30s, you have a one in 233 chance of developing breast cancer. By age 85, your chance is one in eight.
  
  

• A personal history of breast cancer. If you've had breast cancer in one breast, you have an increased risk of developing cancer in the other breast.
  
  

• Family history. If you have a mother, sister or daughter with breast or ovarian cancer or both, or a male relative with breast cancer, you have a greater chance of developing breast cancer. In general, the more relatives you have who were diagnosed with breast cancer before reaching menopause, the higher your own risk.
  
  

• Genetic predisposition. Between 5 per cent and 10 per cent of breast cancers are inherited. Defects in one of several genes, especially BRCA1 or BRCA2, put you at greater risk of developing breast, ovarian and colon cancers. Usually these genes help prevent cancer by making proteins that keep cells from growing abnormally. But if they have a mutation, the genes aren't as effective at protecting you from cancer.
  
  

• Radiation exposure. If you received radiation treatments to your chest as a child or young adult, you're more likely to develop breast cancer later in life. Your risk is greatest if you received radiation as an adolescent during breast development.
  
  

• Excess weight. The relationship between excess weight and breast cancer is complex. In general, weighing more than that which is health increases your risk, particularly if you gained the weight as an adolescent. But the risk is even greater if you put the weight on after menopause. Your risk is also greater if you have more body fat in the upper part of your body.
  
  

• Early onset of menstrual cycles. If you got your period at a young age, especially before age 12, you may have a greater likelihood of developing breast cancer. Experts attribute this risk to the early exposure of the breast tissue to estrogens.