what is breast cancer

Breast cancer is a malignant (cancerous) tumor that starts from cells of the breast. The disease occurs mostly in women, but men can get breast cancer too. The information here refers only to breast cancer in women. There is separate information about breast cancer in men available in the American Cancer Society's document

Normal Breast Structure

In order to understand breast cancer, it is helpful to have some basic knowledge about the normal structure of the breasts, as shown in the picture below.

A woman’s breast is made up of glands that make breast milk (lobules), ducts (small tubes that carry milk from the lobules to the nipple), fatty and connective tissue, blood vessels, and lymph (pronounced limf) vessels. Most breast cancers begin in the cells that line the ducts (ductal cancer), some begin in the lobules (lobular cancer), and the rest in other tissues.



The Lymph System

The lymph system is important because it is one of the ways in which breast cancers can spread. This system has several parts.

Lymph nodes are small, bean-shaped collections of immune system cells that are connected by lymphatic vessels. Lymphatic vessels are like small veins, except that they carry a clear fluid called lymph (instead of blood) away from the breast. Breast cancer cells can enter lymphatic vessels and begin to grow in lymph nodes.

Most lymph vessels of the breast lead to lymph nodes under the arm. These are called axillary (ax-uh-lair-ee) nodes. If breast cancer cells reach the underarm lymph nodes and continue to grow, they cause the nodes to swell. Once cancer cells have reached these nodes they are more likely to spread to other organs of the body too. Knowing whether cancer cells have spread to lymph nodes is important because if they have, there is a higher chance that the cells have also gotten into the bloodstream and spread to other places in the body. This could affect the treatment plan.

Benign Breast Lumps

Most breast lumps are benign (be-nine); that is, they are not cancer. Benign breast tumors are abnormal growths, but they do not spread outside of the breast and they are not life threatening. But some benign breast lumps can increase a woman’s risk of getting breast cancer.

Most lumps turn out to be caused by fibrocystic (fi-bro-sis-tik) changes. Cysts are fluid-filled sacs. Fibrosis is the formation of scar-like tissue. Such changes can cause breast swelling and pain. The breasts may feel lumpy, and sometimes there is a clear or slightly cloudy nipple discharge. For more detail, please see the document,

source: http://www.cancer.org/docroot/CRI/content/CRI_2_2_1X_What_is_breast_cancer_5.asp?sitearea=