What is Breast Cancer?

The breast is a collection of glands and fatty tissue that lies between the skin and the chest wall. The glands inside the breast produce milk after a woman has a baby. Each gland is also called a lobule, and many lobules make up a lobe. There are 15 to 20 lobes in each breast. The milk gets to the nipple from the glands by way of tubes called ducts. The glands and ducts get bigger when a breast is filled with milk, but the tissue that is most responsible for the size and shape the breast is the fatty tissue. There are also blood vessels and lymph vessels in the breast. Lymph is a clear liquid waste product that gets drained out of the breast into lymph nodes. Lymph nodes are small, pea-sized pieces of tissue that filter and clean the lymph. Most lymph nodes that drain the breast are under the arm in what is called the axilla.

What is breast cancer?
Breast cancer happens when cells in the breast begin to grow out of control and can then invade nearby tissues or spread throughout the body. Large collections of this out of control tissue are called tumors. However, some tumors are not really cancer because they cannot spread or threaten someone's life. These are called benign tumors. The tumors that can spread throughout the body or invade nearby tissues are considered cancer and are called malignant tumors. Theoretically, any of the types of tissue in the breast can form a cancer, but usually it comes from either the ducts or the glands. Because it may take months to years for a tumor to get large enough to feel in the breast, we screen for tumors with mammograms, which can sometimes see disease before we can feel it.

Am I at risk for breast cancer?
Breast cancer is the most common malignancy affecting women in North America and Europe. Every woman is at risk for breast cancer. Close to 200,000 cases of breast cancer were diagnosed in the United States in 2001. Breast cancer is the second leading cause of cancer death in American women behind lung cancer. The lifetime risk of any particular woman getting breast cancer is about 1 in 8 although the lifetime risk of dying from breast cancer is much lower at 1 in 28.

Risk factors for breast cancer can be divided into those that you cannot change and those that you can change. Some factors that increase your risk of breast cancer that you cannot alter include being a woman, getting older, having a family history (having a mother, sister, or daughter with breast cancer doubles your risk), having a previous history of breast cancer, having had radiation therapy to the chest region, being Caucasian, getting your periods young (before 12 years old), having your menopause late (after 50 years old), never having children or having them when you are older than 30, and having a genetic mutation that increases your risk. Genetic mutations for breast cancer have become a hot topic of research lately. Between 3% to 10% of breast cancers may be related to changes in either the gene BRCA1 or the gene BRCA2. Women can inherit these mutations from their parents and it may be worth testing for either mutation if a woman has a particularly strong family history of breast cancer (meaning multiple relatives affected, especially if they are under 50 years old when they get the disease). If a woman is found to carry either mutation, she has a 50% chance of getting breast cancer before she is 70. Family members may elect to get tested to see if they carry the mutation as well. If a woman does have the mutation, she can get more rigorous screening or even undergo preventive (prophylactic) mastectomies to decrease her chances of contracting cancer. The decision to get tested is a highly personal one that should be discussed with a doctor who is trained in counseling patients about genetic testing.

Certain factors which increase a woman's risk of breast cancer can be altered including taking hormone replacement therapy (long term use of estrogens with progesterone for menopause symptoms slightly increases your risk), taking birth control pills (a very slight increased risk that disappears in women who have stopped them for over 10 years), not breastfeeding, drinking 2 to 5 alcoholic drinks a day, being overweight (especially after menopause), and not exercising. All of these modifiable risk factors are not nearly as important as gender, age, and family history, but they are things that a woman can control that may reduce her chances of developing a breast malignancy. Remember that all risk factors are based on probabilities, and even someone without any risk factors can still get breast cancer. Proper screening and early detection are our best weapons in reducing the mortality associated with this disease.