Breast cancer is a malignant form of cancer that develops in breast tissue. The most common type of breast cancer begins in the lining of the ducts and is called ductal carcinoma. Another type of breast cancer, called lobular carcinoma, arises in the lobules. The cause of most types of breast cancer is unknown. Breast cancer has been related to two genes, BRC1 and BRC2.
Breast cancer occurs in men as well as women, but is much more common in women.
Studies show that one in 8 or 9 American women will develop breast cancer at some point in life. The risk of breast cancer greatly increases after age 30. The average age of women diagnosed with breast cancer is 60 years. Breast cancer appears to be more frequently in women whose diet is very high in fat. Older women who are overweight are at greater risk.