Types of Breast Cancer
In order to understand breast cancer and how to treat it, it's important to understand how breasts work. Female breasts are supposed to produce milk. In order to do this, breasts are made up of lobules -- glands that produce milk -- and ducts which carry the milk from the lobule to the nipple (when milk is being produced). The ducts and lobules are surrounded by fatty breast tissue.
Breast cancer can form either in the lobules or in the ducts. A cancer that forms in the lobules is known as lobular carcinoma while a cancer that forms in the ducts is known as ductal carcinoma.
The ducts and lobules are connected like branches on a tree trunk, forming a closed system. The only openings out of the system are at the nipple. Thus, a breast cancer that is contained within this closed system is said to be in-situ or non-invasive. A breast cancer that has spread into the surrounding breast tissue is called invasive.
Lymph nodes and breast cancer
The lymphatic system -- made up of lymph nodes -- is part of the circulatory system and an important part of the body's defense against infection. The lymphatic system is made up of a network of lymphatic vessels that carry a clear fluid called "lymph".
In terms of the breast, lymph bathes the tissue of the breast, and then passes through the lymph nodes, where it is filtered, and eventually travels back into the blood stream. There are several areas or chains of lymph nodes that drain the breast. They are located on both sides of the chest bone (internal mammary chain), under your arms (axillary chain), and above your collarbone (supraclavicular chain).
Each breast primarily drains into the axillary lymph node chain under the arm. But occasionally they drain to the other chains of lymph nodes. Once in the lymph nodes, it is filtered of bacteria and other foreign material before it can reach the bloodstream.
Breast cancer cells can break off from the initial tumor and travel to other parts of the body through the lymph fluid (or the blood stream). Once in the lymph fluid, they pass through the lymph nodes and can get trapped. The presence of cancer cells in lymph nodes is an indication that the cancer has the ability to spread and is a more aggressive type of breast cancer. However, some patients (as many as 30%) with lymph nodes testing negative for cancer may have cancer that has spread to another organ (bones, liver, lung etc.) and some patients with lymph nodes testing positive (up to 25%) do not have tumor spread anywhere else. For this reason, examining the lymph nodes for breast cancer is an important step in the evaluation of breast cancer.