Definition

Breast cancer is the most common form of cancer in women and the second most common cause of cancer death for women in the U.S. While the majority of new breast cancers are diagnosed as a result of an abnormality seen on a mammogram, a lump or change in consistency of the breast tissue felt with the fingertips can also be a warning sign of the disease.

Heightened awareness of breast cancer risk in the past decades has led to an increase in the number of women getting mammograms. Breast cancers are being detected in earlier stages and survival rates are going up. Still, breast cancer is the most common cause of death in women between the ages of 45 and 55. Although breast cancer is more common in women, it does occur in men. Male breast cancer accounts for about 1% of all cancer deaths in men.

Breast cancer is caused by the development of malignant cells in the breast. The malignant cells originate in the lining of the milk glands or ducts of the breast (ductal epithelium), defining this malignancy as a cancer. Cancer cells are characterized by uncontrolled division leading to abnormal growth and the ability of these cells to invade normal tissue locally or to spread throughout the body, in a process called metastasis.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). There are numerous types of breast cancer, but cancer that begins in the milk ducts (ductal carcinoma) is the most common type. It occurs in both men and women, although male breast cancer is rare.

Description

Breast cancer arises in the milk- producing glands of the breast tissue. Groups of glands in normal breast tissue are called lobules. The products of these glands are secreted into a duct system that leads to the nipple. Depending on where in the glandular or ductal unit of the breast the cancer arises, it will develop certain characteristics that are used to sub-classify breast cancer into types.

The pathologist will note the subtype at the time of evaluation with the microscope. Ductal carcinoma begins in the ducts, lobular carcinoma has a pattern involving the lobules or glands. The more important classification is related to the evaluated tumor's capability to invade, as this characteristic defines the disease as a true cancer. The stage before invasive cancer is called in situ, meaning that the early malignancy has not yet become capable of invasion. Thus, ductal carcinoma in situ is considered a minimal breast cancer.