Understanding Breast Cancer

Many women do not learn much about breast health unless they breastfeed or they have a problem that needs medical attention. Becoming familiar with breast anatomy and physiology can help you understand the normal changes that occur during your lifetime. This knowledge is a good place to start learning about health problems and conditions that affect the breasts.

The breasts are made up of a complex network of milk-producing sacs, passageways for carrying milk, supporting tissue, lymph nodes, glands, tiny muscles and fat. Throughout puberty and menopause, not only does the look of the breasts change but also the structure and function of the breasts.

This section describes these changes, explains breast cancer and other breast conditions as well as includes basic statistics on breast cancer. Every day, cells in your body divide, grow and die. Most of the time cells divide and grow in an orderly manner. But sometimes cells grow out of control. This kind of growth of cells forms a mass or lump called a tumor. Tumors are either benign or malignant.

Benign [bee-NINE] tumors

Benign tumors are not cancerous. But left untreated, some can pose a health risk, so they are often removed. When these tumors are removed, they typically do not reappear. Most importantly, the cells of a benign tumor do not invade nearby tissue or spread to other parts of the body.

Malignant [ma-LIG-nant] (cancerous) tumors

Malignant tumors are made of abnormal cells. Malignant tumor cells can invade nearby tissue and spread to other parts of the body. A malignant tumor that develops in the breast is called breast cancer.

How does breast cancer grow and spread?

To continue growing, malignant breast tumors need to be fed. They get nourishment by developing new blood vessels in a process called angiogenesis. The new blood vessels supply the tumor with nutrients that promote growth. As the malignant breast tumor grows, it can expand into nearby tissue. This process is called invasion. Cells can also break away from the primary, or main, tumor and spread to other parts of the body. The cells spread by traveling through the blood stream and lymphatic system. This process is called metastasis. When malignant breast cells appear in a new location, they begin to divide and grow out of control again as they create another tumor. Even though the new tumor is growing in another part of the body, it is still called breast cancer. The most common locations of breast cancer metastases are the lymph nodes, liver, brain, bones and lungs.

Breast cancer growth

The light circles represent normal breast cells and the dark-shaded circles represent cancerous breast cells. As the cancerous cells grow and multiply, they develop into a malignant tumor within the breast.


Why does breast cancer grow?

We all have genes that control the way our cells divide and grow. When these genes do not work like they should, a genetic error, or mutation, has occurred. Mutations may be inherited or spontaneous. Inherited mutations are ones you were born with — an abnormal gene that one of your parents passed on to you at birth. Inherited mutations of specific genes, such as the BRCA1 and BRCA2 genes, increase a woman’s risk of developing breast cancer. Spontaneous mutations occur within your body during your lifetime. The actual cause or causes of mutations still remains unknown. Researchers have identified two types of genes that are important to cell growth. Errors in these genes turn normal cells into cancerous ones.