Breast Cancer Overview
Breast cancer is cancer arising in breast tissue. Cancer is simply a group of abnormal cells that have abnormal growth patterns.
- Although breast cancer is primarily a disease of women, about 1% of breast cancers occur in men.
- Breast cancer is the most common type of
cancer in women with the exception of nonmelanoma skin cancers. It is the second
leading cause of death by cancer in women, following only lung cancer.
- In 2011, the American Cancer Society estimated that 230,480 new cases of invasive breast cancer would be diagnosed among women in the United States and that a further 57,650 new cases of in-situ (noninvasive) breast cancer would be diagnosed.
- A woman has a lifetime risk of developing invasive breast cancer of about
one in eight, or 13%.
- Death rates from breast cancer have been gradually declining and continue
to decline. These decreases are likely due both to increased awareness and
screening and improved treatment methods.
- There are currently about 2.5 million breast cancer survivors in the U.S.
The breasts are made of fat, glands,
and connective (fibrous) tissue. The breast has several lobes, which are divided
into lobules that end in the milk glands. Tiny ducts run from the many tiny
glands, connect together, and end in the nipple.
- These ducts are where 80% of breast cancers occur. Breast cancer that arises in the ducts is called ductal cancer.
developing in the lobules is termed lobular cancer. About 10%-15% of breast
cancers are of this type.
- Other less common types of breast cancer include
inflammatory breast cancer, medullary cancer, phyllodes tumor, angiosarcoma,
mucinous (colloid) carcinoma, mixed tumors, and a type of cancer involving the
nipple termed Paget's disease.
Precancerous changes, called in situ changes, are
- In situ is Latin for "in place" or "in site" and means that the
changes haven't spread from where they started.
- When these in situ changes occur in the ducts, they are called ductal
carcinoma in situ (DCIS). DCIS may be identified on routine mammography.
- When in-situ changes happen in the lobules, it is called lobular carcinoma
in situ (LCIS).
When cancers spread into the surrounding tissues, they are
termed infiltrating cancers. Cancers spreading from the ducts into adjacent
spaces are termed infiltrating ductal carcinomas. Cancers spreading from the
lobules are infiltrating lobular carcinomas.
The most serious cancers are
metastatic cancers. Metastasis means that the cancer has spread from the place
where it started into other tissues distant from the original tumor site. The
most common place for breast cancer to metastasize is into the lymph nodes under
the arm or above the collarbone on the same side as the cancer. Other common
sites of breast cancer metastasis are the brain, the bones, and the liver.
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