Ask a Doctor
First of all, my best wishes to your friend, and I hope her treatment is successful. Second, there are more than three types of breast cancer; there are two more common types, and then a grab-bag of rarer subtypes with different causes and implications.
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.
- 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 common.
- 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.
- Lobular carcinoma in situ (LCIS) refers to abnormal-appearing cells in the milk-producing lobules of the breast. This is considered to be a condition that increases a woman's risk for breast cancer.
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 and dangerous 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. Cancers which have spread only into the lymph nodes under the arm may still be cured. Those which spread to more distant lymph nodes or other organs are not usually curable with available treatments today. Treatments can extend lives for years even in these cases.
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"HER2 Testing for Breast Cancer." Cancer.net. <http://www.cancer.net/research-and-advocacy/asco-care-and-treatment-recommendations-patients/her2-testing-breast-cancer>.
United States. National Cancer Institute. "General Information About Breast Cancer." Sept. 25, 2014. <http://www.cancer.gov/cancertopics/pdq/
United States. National Cancer Institute. "SEER Stat Fact Sheets: Breast Cancer." <http://seer.cancer.gov/statfacts/html/