Breast cancer is a malignant tumor that originates in cells of the breast. Most breast cancers begin in the cells that line the ducts, some begin in the lobules (lobular cancer), and the rest occur in other tissues. The point of origin is determined by the microscopic appearance of cancer cells that have been removed by biopsy.
Ductal and lobular carcinomas are further subdivided into in situ and invasive breast cancers. In situ breast cancer means that the cancer cells have not invaded breast tissue around the duct or lobe; the cells are contained within their place of origin. Invasive (infiltrating) breast cancers are those that break free from the point of origin and invade the surrounding tissues that support the ducts and lobules.
Invasive (infiltrating) ductal carcinoma is the most common breast cancer, it accounts for about 80% of invasive breast cancers. It starts in a milk duct, breaks through the wall of the duct, and invades the tissue of the breast. From there it can spread to other parts of the body.
There are a variety of other less common types of breast cancers, including triple negative breast cancer, inflammatory breast cancer, medullary carcinoma, mucinous (colloid) carcinoma, Paget’s disease of the nipple, tubular carcinoma, phyllodes tumor, metaplastic carcinoma, sarcoma, papillary carcinoma, angiosarcoma, and adenoid cystic carcinoma.
They are mainly related to the total estrogenic events during the patient's life, the genetic background, the environment, or the life style
However, multiple risk factors for the disease have been identified:
Some studies suggest that increased physical activity and breast feeding, especially for one and a half to two years, are linked to decreased risk of developing breast cancer.