A woman's breast is made up of milk glands and milk ducts, surrounded by fatty tissue and connective supports. Uncontrolled growth of cells in any of these breast tissues can cause breast cancer.
Breast cancer is the most common cancer among women. It tends to occur at an earlier age than do other cancers or heart attacks and strokes. Chances of developing breast cancer rise dramatically as women age: 13 out of 1,000 women in their 40s; 23 out of 1,000 women in their 50s; 29 out of 1,000 women in their 60s; 31 out of 1,000 women in their 70s.
Breast cancer is rare in men, accounting for less than 1% of all cases. Breast cancer is the second most common cause of death from cancer in women.