What is breast cancer?

Understanding the basics of breast cancer is an important early step in coming to grips with your new diagnosis. The breast is made up of cells which under normal condition divide and form new cells in an orderly fashion. In cancer, the cells divide in an uncontrolled fashion. By definition cancer is uncontrolled cell growth. In the early stage the cells remain in the milk producing glands (lobules, which make milk) or the dsucts (tubes which transport milk from the glands to the nipple). When the cancer cells are confined to the ducts or lobules the cancer is referred to as in-situ or non-invasive. These in-situ or non-invasive cancers are usually incapable of leaving the breast. With time some cancers develop the ability to penetrate the lining of the ducts and invade into the surrounding tissue. Tumors that have invaded the lining of the duct are called invasive or infiltrative cancers. This only means they are capable of leaving the breast. As the invasive tumors grow they eventually can invade into the surrounding lymphatic or blood vessels of the breast. Once they have invaded these structures they can spread (metastasize) to other sights in the body. The usual first sight of metastasis is the under arm (axillary) lymph nodes. Cells can also spread to other organs of the body. The most common sites for distant metastasis are the bones, the liver, or the lung.