Breast cancer is a disease in which cancerous cells form in the breast area.
The breast is made up of lobes and ducts. Each breast has sections of lobes that contain smaller sections called lobules. Lobules end in clusters of tiny bulbs that can produce milk. The lobes, lobules and bulbs are linked by thin ducts.
Breasts also have blood and lymph vessels. The lymph vessels carry lymph fluid and lead to organs called lymph nodes. Lymph nodes are small bean-shaped structures found throughout the body. They filter substances in lymph and help fight infection and disease. Clusters of lymph nodes are found near the breast, underarm, collarbone and in the chest.
The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma and is the type more often found in both breasts.
Age and health history can affect the risk of developing breast cancer as can these other factors:
- Over 50
- Menstruating at an early age
- Older when you first gave birth or never have given birth
- A personal history of breast cancer or benign (non-cancerous) breast disease
- A mother or sister with breast cancer
- Treatment with radiation therapy to the breast/chest
- Breast tissue that is dense on a mammogram
- Hormone use (such as estrogen and progesterone)
- Drinking alcoholic beverages
- Being Caucasian
- Genetic predisposition
Hereditary breast cancer makes up approximately 5 percent to 10 percent of all breast cancers.
Women who have an altered gene related to breast cancer and who have had breast cancer in one breast have an increased risk of developing breast cancer in the other breast. These women also have an increased risk of developing ovarian and other cancers. Men who have an altered gene related to breast cancer also have an increased risk of developing this disease.
Genetic tests can identify those with a genetic predisposition for breast cancer.
Inflammatory breast cancer
In inflammatory breast cancer (IBC), the breast looks red and swollen and feels warm. The redness and warmth occur because the cancer cells block the lymph vessels in the skin. The skin of the breast may also have a pitted appearance like the skin of an orange.
Recurrent breast cancer
Recurrent breast cancer is cancer that has recurred after it has been treated. The cancer may come back in the breast, in the chest wall or in other parts of the body.
Stages of breast cancer
After breast cancer has been diagnosed, tests are done to find out if cancer cells have spread within the breast or to other parts of the body. (Learn more about diagnostic testing.)
The process used to find out whether the cancer has spread within the breast or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.
The following stages are used for breast cancer:
Stage 0 (carcinoma in situ)
There are two types of breast carcinoma in situ:
- Ductal carcinoma in situ (DCIS) is a noninvasive, precancerous condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive.
- Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules of the breast. This condition seldom becomes invasive cancer; however, having lobular carcinoma in situ in one breast increases the risk of developing breast cancer in either breast.
In stage I, the tumor is two centimeters or smaller and has not spread outside the breast.
In stage IIA:
- No tumor is found in the breast, but cancer is found in the axillary lymph nodes (the lymph nodes under the arm); or
- The tumor is two centimeters or smaller and has spread to the axillary lymph nodes; or
- The tumor is between two and five centimeters but has not spread to the axillary lymph nodes.
In stage IIB, the tumor is either:
- Between two and five centimeters and has spread to the axillary lymph nodes; or
- Larger than five centimeters but has not spread to the axillary lymph nodes.
Stage IIIA to IIIB
In stage IIIA:
- No tumor is found in the breast, but cancer is found in axillary lymph nodes that are attached to each other or to other structures; or
- The tumor is five centimeters or smaller and has spread to axillary lymph nodes that are attached to each other or to other structures; or
- The tumor is larger than five centimeters and has spread to axillary lymph nodes that may or may not be attached to each other or to other structures.
In stage IIIB, the cancer may be any size and:
- Has spread to tissues near the breast (the skin or chest wall, including the ribs and muscles in the chest); and
- May have spread to lymph nodes within the breast or under the arm.
Stage IIIC to IV
In stage IIIC, the cancer:
- Has spread to lymph nodes beneath the collarbone and near the neck; and
- May have spread to lymph nodes within the breast or under the arm and to tissues near the breast.
Is considered operable if it:
- is found in 10 or more of the lymph nodes under the arm; or
- is found in the lymph nodes beneath the collarbone and near the neck on the same side of the body as the breast with cancer; or
- is found in lymph nodes within the breast itself and in lymph nodes under the arm.
Is considered inoperable if:
- the cancer has spread to the lymph nodes above the collarbone and near the neck on the same side of the body as the breast with cancer.
In stage IV, the cancer has spread to other organs of the body, most often the bones, lungs, liver or brain.