Breast cancers are malignancies that develop in the tissues of one or both breasts. Breast cancer is the most common cancer among women in the United States, other than Skin Cancer.
There are two main types of breast cancer:
- Ductal carcinoma is the most common breast cancer and starts in the tubes, or ducts, that move milk from the breast to the nipple.
- Lobular carcinoma originates from the lobules which produce milk.
Breast cancer can be invasive or noninvasive:
Invasive breast cancers includes cancers which have spread from the milk duct or lobule to other tissues in the breast.
- Representing 10-15% of invasive breast cancers, invasive ductal carcinoma occurs when cancer cells spread beyond the basement membrane, which covers the underlying connective tissue in the breast.
- Invasive lobular carcinoma describes 70-80% of breast cancers which spread through the wall of the milk producing lobule, and are characterized by branch-like growing patterns.
Noninvasive refers to breast cancer that has not invaded other breast tissue.
- Noninvasive breast cancers include Lobular carcinoma in situ (LCIS) and Ductal carcinoma in situ (DCIS).
Some breast cancers are sensitive to the hormone estrogen, which causes breast cancer to grow. These cancers have estrogen receptors and are called ER-positive cancer.
Some breast cancers are HER2-positive, which refers to a gene that helps cells to grow, divide and repair themselves faster than normal.