Classifications of Breast Cancer
Most breast cancer develops in glandular tissue and is classified as adenocarcinoma. The earliest form of the disease, ductal carcinoma in situ (DCIS), develops solely in the milk ducts. The most common type of breast cancer, invasive ductal carcinoma (IDC), develops from DCIS, spreads through the duct walls, and invades the breast tissue. Invasive ductal carcinoma also is called infiltrating ductal carcinoma.
Invasive lobular carcinoma originates in the milk glands and accounts for 1015 percent of invasive breast cancers. Less common types of breast cancer include the following:
- Inflammatory (breast tissue is warm and appears red; tends to spread quickly)
- Medullary carcinoma (originates in central breast tissue)
- Mucinous carcinoma (invasive; usually occurs in postmenopausal women)
- Paget's disease of the nipple (originates in the milk ducts and spreads to the skin of the nipples or areola)
- Phyllodes tumor (tumor with a leaf-like appearance that extends into the ducts; rarely metastasizes)
- Tubular carcinoma (small tumor that is often undetectable by palpation)
Rarely, sarcomas (cancer of the connective tissue) and lymphomas (cancer of the lymph tissue) develop in the breasts.