Breast cancer is a cancer that starts in the tissues of the breast.
There are two main types of breast cancer:
- Ductal carcinoma starts in the tubes (ducts) that move milk from the breast to the nipple. Most breast cancers are of this type.
- Lobular carcinoma starts in parts of the breast, called lobules, that produce milk.
In rare cases, breast cancer can start in other areas of the breast.
Many breast cancers are sensitive to the hormone estrogen. This means that estrogen causes the breast cancer tumor to grow. Such cancer is called estrogen receptor positive cancer or ER positive cancer.
Some women have what's called HER2-positive breast cancer. HER2 refers to a gene that helps cells grow, divide, and repair themselves. When cells have too many copies of this gene, cells -- including cancer cells -- grow faster. Experts think that women with HER2-positive breast cancer have a more aggressive disease and a higher risk of recurrence than those who do not have this type.
Alternative Names
Cancer - breast; Carcinoma - ductal; Carcinoma - lobular
Causes, incidence, and risk factors
Over the course of a lifetime, 1 in 8 women will be diagnosed with breast cancer.
Risk factors you cannot change include:
- Age and gender -- Your risk of developing breast cancer increases as you get older. The majority of advanced breast cancer cases are found in women over age 50. Women are 100 times more likely to get breast cancer then men.
- Family history of breast cancer -- You may also have a higher risk for breast cancer if you have a close relative has had breast, uterine, ovarian, or colon cancer. About 20 - 30% of women with breast cancer have a family history of the disease.
- Genes -- Some people have genes that make them more prone to developing breast cancer. The most common gene defects are found in the BRCA1 and BRCA2 genes. These genes normally produce proteins that protect you from cancer. But if a parent passes you a defective gene, you have an increased risk for breast cancer. Women with one of these defects have up to an 80% chance of getting breast cancer sometime during their life.
- Menstrual cycle -- Women who get their periods early (before age 12) or went through menopause late (after age 55) have an increased risk for breast cancer.
