What is Breast Cancer?
Breast cancer is a malignant tumor that has developed from cells of the breast. The disease occurs mostly in women, but does occur rarely in men. The remainder of this document refers only to breast cancer in women. A separate document on male breast cancer is also available from the American Cancer Society.
Normal breast structure
The main components of the female breast are lobules (milk-producing glands), ducts (milk passages that connect the lobules and the nipple), and stroma (fatty tissue and ligaments surrounding the ducts and lobules, blood vessels, and lymphatic vessels).
Lymphatic vessels are similar to veins, except that they carry lymph instead of blood. Lymph is a clear fluid that contains tissue waste products and immune system cells that are on their way from areas of infection. Cancer cells can enter lymph vessels. Most lymphatic vessels of the breast lead to auxillary (underarm) lymph nodes.
Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections. When breast cancer cells reach the auxillary lymph nodes, they can continue to grow, often causing swelling of the lymph nodes in the underarm area. If breast cancer cells have grown in the auxillary lymph nodes, they are more likely to have spread to other organs of the body as well. This is why finding out whether breast cancer has spread to auxillary lymph nodes is important in selecting the best mode of treatment.
Benign breast lumps
Most breast lumps are benign, that is, not cancerous. Most lumps are caused by fibrocystic changes. Cysts are fluid-filled sacs, and fibrosis refers to connective tissue or scar tissue formation. Breast swelling and pain can be associated with fibrocystic changes. The breasts may feel nodular, or lumpy, and, sometimes, a clear or slightly cloudy nipple discharge is present. Benign breast tumors such as fibroadenomas or papillomas are abnormal growths but, they cannot spread outside of the breast to other organs. They are not life-threatening.
What are the Key Statistics About Breast Cancer
Breast cancer is the most common cancer among women, excluding skin cancers. The American Cancer Society estimates that in 1999 about 175,000 new cases of invasive breast cancer will be diagnosed among women in the United States. An estimated 1,300 cases will be diagnosed among men.
The breast cancer incidence rate, a measure of the number of new breast cancers per 100,000 women, increased by about 4% per year during the 1980s but during the past few years, incidence has leveled off.
In 1999, there will be about 43,700 deaths from breast cancer in the United States, 43,300 among women, and 400 among men. Breast cancer is the second leading cause of cancer death in women, second only to lung cancer. It is the leading cause of cancer death among women aged 40 to 55. The breast cancer mortality rate, a measure of breast cancer deaths per 100,000 women, has been decreasing during the past few years. Increased screening of women, leading to detection of cancers at an earlier stage, and more effective treatments, are most likely responsible for lowering the breast cancer mortality rate.
Reprinted from the American Cancer Society’s website, http://www.cancer.org. The American Cancer Society is the nationwide community-based voluntary healthy organization dedicated to eliminating cancer as a major health problem by preventing cancer, saving lives and diminishing suffering from cancer, through research, education, advocacy and service.