Type 2 diabetes has been shown to be a risk factor for breast cancer in Western cultures.
Researchers at the Second Hospital of Shandong University in Jian, China, carried out a study to determine risk factors for breast cancer in their society.
Their study, published in PLoS One in July 2012, included:

• 122,058 women in eastern China.
  
• a total of 320 were diagnosed with breast cancer.
  

Those with a history of diabetes had more than three and a half times higher risk of developing cancer in their breast than those without Type 2 diabetes.
Other factors included:

• age,
• family history,
• a history of benign lumps,
• poor overall life satisfaction,
• body mass,
• poverty,
• miscarriages and abortions, and
• infrequent consumption of garlic.
  

Ninety-one per cent of women diagnosed with breast cancer were over 35 years of age and 60 per cent were pre-menopausal...

• those with a family history of this form of cancer were more than five times more likely to be diagnosed with this type of cancer than those without a family history.
  
• women with a history of benign breast tumors had a 13 per cent increased risk of breast cancer.
  
• participants with poor overall life satisfaction had more than twice the risk of breast cancer as those with good life satisfaction.
  
• women with a high body mass index, multiple miscarriages or abortions, or poor financial status had about a 50 per cent increased risk of breast cancer.
  
• women who consumed small amounts of garlic had a 23 per cent higher risk of this type of cancer than those who ate higher amounts of it.
  

Women have no control over their age, family history, or genetics.
Prevention or control of diabetes and obesity are two things they can control.
See your doctor or dietitian for guidance re a healthful, low-calorie diet and the type of exercise that will prevent diabetes or keep it under control.
Normalizing weight is important for more than cosmetic reasons.
It could help to prevent Type 2 diabetes and breast cancer.
Performing self breast exams is no longer recommended.
It was found women who performed them frequently found benign masses leading to expensive tests that turned out to be unnecessary.
The American Cancer Society recommends:

• yearly mammograms for women beginning at age 40, and
• clinical breast exams every three years for women in their 20's and 30's, increasing to every year for women 40 and over.
  

Women should know the shape and size of their breasts and report changes to their doctors promptly so further testing can be carried out.
If breast cancer is detected early, its 5-year survival rate is 99 per cent.
The rate goes down if the cancer has had time to grow and spread.
If it has spread to distant organs, the 5-year survival rate is only 14 per cent, so early detection is important.