This technique is rapidly becoming a standard part of surgical evaluation of many types of breast cancer. The first site to which a breast cancer usually spreads is the lymph nodes in the axilla (underarm area). In the past, surgeons have often needed to remove a large number of lymph nodes from this area as part of surgery for breast cancer. While this was very helpful to guide patient treatment, it could lead to complications such as arm swelling.
The theory behind sentinel lymph node mapping is that the lymph nodes which drain the breast are organized like a chain and that if the cancer has not spread to the first lymph node in the chain, it will not have spread beyond it. To perform sentinel lymph node mapping, a small amount of an isotope (a slightly radioactive liquid) is injected into the breast containing the cancer. Images are then taken to identify the first lymph node (or nodes) to which the isotope spreads. At the time of surgery, the surgeon is guided to these lymph nodes and he or she removes these and tests them first. If no tumor has spread to the “sentinel” node(s), the patient does not need to have any more lymph nodes removed and therefore has a much lower chance of complications.
One important fact for sentinel lymph node mapping patients to remember is that just because a lymph node “lights up” on a scan does NOT mean that the lymph node contains tumor. It simply shows where the tumor would likely spread if it were going to spread.