Breast cancer is an uncontrolled growth of breast cells. To better understand breast cancer, it helps to understand how any cancer can develop.
Cancer occurs as a result of mutations, or abnormal changes, in the genes responsible for regulating the growth of cells and keeping them healthy. The genes are in each cellís nucleus, which acts as the "control room" of each cell. Normally, the cells in our bodies replace themselves through an orderly process of cell growth: healthy new cells take over as old ones die out. But over time, mutations can "turn on" certain genes and "turn off" others in a cell. That changed cell gains the ability to keep dividing without control or order, producing more cells just like it and forming a tumor.
A tumor can be benign (not dangerous to health) or malignant (has the potential to be dangerous). Benign tumors are not considered cancerous: their cells are close to normal in appearance, they grow slowly, and they do not invade nearby tissues or spread to other parts of the body. Malignant tumors are cancerous. Left unchecked, malignant cells eventually can spread beyond the original tumor to other parts of the body.
The term "breast cancer" refers to a malignant tumor that has developed from cells in the breast. Usually breast cancer either begins in the cells of the lobules, which are the milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. Less commonly, breast cancer can begin in the stromal tissues, which include the fatty and fibrous connective tissues of the breast.
Larger Version - Over time, cancer cells can invade nearby healthy breast tissue and make their way into the underarm lymph nodes, small organs that filter out foreign substances in the body. If cancer cells get into the lymph nodes, they then have a pathway into other parts of the body. The breast cancerís stage refers to how far the cancer cells have spread beyond the original tumor (see Stages of Breast Cancer table for more information).
Breast cancer is always caused by a genetic abnormality (a "mistake" in the genetic material). However, only 5-10% of cancers are due to an abnormality inherited from your mother or father. About 90% of breast cancers are due to genetic abnormalities that happen as a result of the aging process and the "wear and tear" of life in general.
While there are steps every person can take to help the body stay as healthy as possible (such as eating a balanced diet, not smoking, limiting alcohol, and exercising regularly), breast cancer is never anyone's fault. Feeling guilty, or telling yourself that breast cancer happened because of something you or anyone else did, is not productive.
Stages of Breast Cancer
Stage 0 Cancer cells remain inside the breast duct, without invasion into normal adjacent breast tissue.
Stage I Cancer is 2 centimeters or less and is confined to the breast (lymph nodes are clear).
Stage IIA No tumor can be found in the breast, but cancer cells are found in the axillary lymph nodes (the lymph nodes under the arm) OR the tumor measures 2 centimeters or smaller and has spread to the axillary lymph nodes OR the tumor is larger than 2 but no larger than 5 centimeters and has not spread to the axillary lymph nodes.
Stage IIB The tumor is larger than 2 but no larger than 5 centimeters and has spread to the axillary lymph nodes OR the tumor is larger than 5 centimeters but has not spread to the axillary lymph nodes.
Stage IIIA No tumor is found in the breast. Cancer is found in axillary lymph nodes that are sticking together or to other structures, or cancer may be found in lymph nodes near the breastbone OR the tumor is any size. Cancer has spread to the axillary lymph nodes, which are sticking together or to other structures, or cancer may be found in lymph nodes near the breastbone.
Stage IIIB The tumor may be any size and has spread to the chest wall and/or skin of the breast AND may have spread to axillary lymph nodes that are clumped together or sticking to other structures, or cancer may have spread to lymph nodes near the breastbone. Inflammatory breast cancer is considered at least stage IIIB.
Stage IIIC There may either be no sign of cancer in the breast or a tumor may be any size and may have spread to the chest wall and/or the skin of the breast AND the cancer has spread to lymph nodes either above or below the collarbone AND the cancer may have spread to axillary lymph nodes or to lymph nodes near the breastbone.
Stage IV The cancer has spread - or metastasized - to other parts of the body.
Breast Cancer Statistics
Breast cancer incidence in women in the United States is 1 in 8 (about 13%). In 2008, an estimated 182,460 new cases of invasive breast cancer are expected to be diagnosed in women in the U.S., along with 67,770 new cases of non-invasive (in situ) breast cancer. About 1,990 new cases of invasive breast cancer will be diagnosed in men in 2008. Less than 1% of all new breast cancer cases occur in men.
From 2001 to 2004, breast cancer incidence rates in the U.S. decreased by 3.5% per year. One theory is that this decrease was due to the reduced use of hormone replacement therapy (HRT) by women after the results of a large study, called the Womenís Health Initiative, were published in 2002. These results suggested a connection between HRT and increased breast cancer risk.
About 40,480 women in the U.S. are expected to die in 2008 from breast cancer, though death rates have been decreasing since 1990. These decreases are thought to be the result of treatment advances, earlier detection through screening, and increased awareness.
For women in the U.S., breast cancer death rates are higher than those for any other cancer besides lung cancer. Besides skin cancer, breast cancer is the most commonly diagnosed cancer among U.S. women. More than 1 in 4 cancers are breast cancer.
Compared to African American women, white women are slightly more likely to develop breast cancer, but less likely to die of it. One possible reason is that African American women tend to have more aggressive tumors, although why this is the case is not known. Women of other ethnic backgrounds - Asian, Hispanic, and Native American - have a lower risk of developing and dying from breast cancer than white women and African American women.
As of 2008, there are about 2.5 million women in the U.S. who have survived breast cancer. A womanís risk of breast cancer approximately doubles if she has a first-degree relative (mother, sister, daughter) who has been diagnosed with breast cancer. About 20-30% of women diagnosed with breast cancer have a family history of breast cancer.
About 5-10% of breast cancers are caused by gene mutations inherited from oneís mother or father. Mutations of the BRCA1 and BRCA2 genes are the most common. Women with these mutations have up to an 80% risk of developing breast cancer during their lifetime, and they often are diagnosed at a younger age (before age 50). An increased ovarian cancer risk is also associated with these genetic mutations. Men with a BRCA1 mutation have a 1% risk of developing breast cancer by age 70 and a 6% risk when they have a BRCA2 mutation.
About 90% of breast cancers are due not to heredity, but to genetic abnormalities that happen as a result of the aging process and life in general. The most significant risk factors for breast cancer are gender (being a woman) and age (growing older).
Symptoms of Breast Cancer
Initially, breast cancer may not cause any symptoms. A lump may be too small for you to feel or to cause any unusual changes you can notice on your own. Often, an abnormal area turns up on a screening mammogram (x-ray of the breast), which leads to further testing.
In some cases, however, the first sign of breast cancer is a new lump or mass in the breast that you or your doctor can feel. A lump that is painless, hard, and has uneven edges is more likely to be cancer. But sometimes cancers can be tender, soft, and rounded. So it's important to have anything unusual checked by your doctor.
According to the American Cancer Society, any of the following unusual changes in the breast can be a symptom of breast cancer:
Swelling of all or part of the breast
These changes also can be signs of less serious conditions that are not cancerous, such as an infection or a cyst. Itís important to get any breast changes checked out promptly by a doctor.
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