Overview

Breast cancer is a type of cancer in which cells in the breast become abnormal and grow and divide uncontrollably.

Normal cells divide, grow, and die on a continual, controlled basis. The nucleus of each cell contains genes made up of DNA that 'tells' that cell what to do and determines its lifespan. When cells grow uncontrollably, they will eventually form a mass, also called a tumor. Benign tumors are not cancer; they do not invade other types of tissue.

Malignant tumors are made up of abnormal cells that are capable of invading nearby tissues. Cells from the original tumor may also break off and travel via the blood or lymph systems to distant location (metastasize). When these cancer cells grow in another organ, the cancer will still be named for the organ where it began. For example, if breast cancer cells travel to the liver and grow there, that person would have metastasized breast cancer, not liver cancer.

How Cancer Grows

Cancer cells grow and divide at an abnormally rapid rate, so they need extra nutrients. Since cells get their requirements supplied by the blood, malignant tumors build new blood vessels - a process called angiogenesis. Developing treatments to stop this process (called anti-angiogenesis) is one promising area of cancer research.

What Causes the Cells To Grow Uncontrollably?

A change or mutation in the genes of a cell changes the way that cells acts. The mutation may exist at birth from an inherited genetic trait from a mother or father or it may be spontaneous - a change that occurs sometime after birth. Inheriting the BRCA1 or BRCA2 gene has been identified as a factor in raising the risk of developing breast cancer.

What Is an Oncogene?

Researchers have identified two genes that control cell grow and division. One is called an oncogene, which gives the command to grow and divide; think of it as the "on" switch. The other is called a tumor-suppressor gene, which tells the cell to stop growing and dividing (think of this as the "off" switch). If the oncogene doesn't stop giving its "on" command or the tumor suppression gene doesn't give its "off" command, the cell will grow & divide uncontrollably.

Occurrence of Breast Cancer

The majority (over 75%) of breast cancers begin in the (milk) ducts within the breast; the next most common site is the lobules - the glandular tissue that makes milk. Most breast cancers are slow-growing and by the time a lump can be felt, it may have been growing for 5 or 10 years. Early breast cancer usually has no symptoms and the earlier a tumor is found, the better the chance of survival. For these reasons it is extremely important for women to be screened regularly by mammography or ultrasound since they may identify a cancerous tumor before it can be felt. In addition, if a lump or thickening can be felt, it is vital to seek a medical evaluation right away.