Why are the lymph nodes important?
A fluid called lymph flows through the lymph glands. Lymph is similar to blood and contains white blood cells, proteins, fats, and other substances. The lymph system helps drain bacteria and other harmful substances from the body. Sometimes, cancer cells can break off from a tumor and enter the lymph. As the fluid flows through the lymph nodes that are near the tumor, the cancer cells can get trapped in the lymph node and begin to grow there. The first lymph nodes that the fluid from the tumor flows into are called the “sentinel lymph nodes.” A sentinel is someone who stands guard. You can think of the sentinel lymph node as the gatekeeper to the rest of the lymph nodes. If the sentinel lymph node has cancer cells in it, there is a chance that the cancer has spread. If the sentinel node does not have cancer cells, the other lymph nodes in that area are probably also cancer-free, and the cancer probably has not spread.
