What is women breast cancer

Breast cancer starts when cells in the breast begin to grow out of control. These cells usually form a tumor that can often be seen on an x-ray or felt as a lump. The tumor is malignant "cancerous" if the cells can grow into (invade) surrounding tissues or spread "metastasize" to distant areas of the body. Breast cancer occurs almost entirely in women, but men can get it, too.

Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how all cancers start and spread, see What Is Cancer?

Breast cancers can start from different parts of the breast. Most breast cancers begin in the ducts that carry milk to the nipple (ductal cancers).

A small number of cancers start in other tissues in the breast. These cancers are called sarcomas and lymphomasand are not really thought of as breast cancers.

How Breast Cancer Spread

The lymph system includes lymph nodes, lymph vessels and lymph fluid found throughout the body. Lymph nodes are small, bean-shaped collections of immune system cells that are connected by lymph "or lymphatic" vessels. Lymph vessels are like small veins, except that they carry a clear fluid called lymph "instead of blood" away from the breast. Lymph contains tissue fluid and waste products, as well as immune system cells. Breast cancer cells can enter lymph vessels and begin to grow in lymph nodes.

Most of the lymph vessels of the breast drain into: 

* Lymph nodes under the arm (axillary nodes).
* Lymph nodes inside the chest near the breast bone (internal mammary lymph nodes)
* Lymph nodes around the collar bone (supraclavicular and infraclavicular lymph nodes)