Ultimately the tumor can spread to vital organs such as the liver, brain, lungs, and spine. About one in eight women in develop breast cancer. The cause of breast cancer is not known. Any woman can have breast cancer. Although it is much less common, men too can have breast cancer.
Some women are more likely to develop breast cancer than others.
There is no definite evidence yet that use of birth control pills for a long period of time causes breast cancer, but this possibility continues to be studied. It also appears that taking estrogen after menopause causes a slight increased risk of breast cancer. Researchers are also studying some viruses as a possible cause. Most often the first sign of breast cancer is a small lump in the breast. The lump is usually painless.