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Breast Cancer Treatment

Surgery: Sentinel Lymph Node Mapping

Lymph fluid drains from the site of the tumor to one or two lymph nodes first before going to the other nodes. The "sentinel node" is the first lymph node to which a tumor drains, and therefore is the first place to which cancer is likely to spread.

In breast cancer, the sentinel node is usually located in the axillary nodes, the group of lymph nodes under the arm. However, in a small percentage of cases, the sentinel node is found elsewhere in the lymphatic system of the breast. In some cases, there can be more than one sentinel node.

How do doctors find the sentinel lymph node?

There are two methods for finding the sentinel node. One is to inject a blue dye near the breast tumor and track its path through the lymph nodes. The dye accumulates in the sentinel node. The injection of the blue dye is done at the time of the surgery, in the operating room.

In a similar technique, doctors inject a safe, small amount of a weak radioactive solution near the tumor. A hand-held probe (which is like a Geiger counter) is then used to find the "hot-spot," or the node in which the weak radioactive solution has accumulated. In contrast to the blue dye, the radioactive tracer is injected a few hours before the surgery (it takes longer for the tracer to get to the lymph node than the blue dye). NOTE: The radioactive solution is harmless. You can be in contact with others after the injection.

At the University of Michigan, these two techniques are used together. This increases that chance that the sentinel lymph node will be found.

What are the advantages of a sentinel lymph node biopsy?

The advantages are many. There is no need to stay overnight in the hospital, there are no drains and physical therapy exercises are usually not necessary. A sentinel lymph node biopsy can lead to a more accurate evaluation of whether the cancer has spread to the lymph nodes. In a traditional axillary lymph node dissection, the pathologist reviews 10 or more lymph nodes and there is no way to tell which one is the sentinel node. When the pathologist receives only 1 or 2 nodes, more cuts can be made through that node to look for cancer. A negative sentinel lymph node indicates a less than 95% chance that the remaining lymph nodes in the axilla are also cancer free.

What are the side effects of sentinel lymph node biopsy?

Side effects of sentinel node biopsy can include minor pain or bruising at the biopsy site and the rare possibility of an allergic reaction to the blue dye used in finding the sentinel node.

The blue dye used in the sentinel lymph node mapping is eliminated from your body in your urine. This changes the color of your urine to blue-green for the day after the procedure. This causes no harm. Also, the area of the breast, which is injected with blue dye, will have a blue color to it. Many women described the area as looking like a blue bruise. It will lessen with time, although it will be visible for several weeks to several months after the procedure.

Some women may experience numbness under the arm or lymphedema after the sentinel lymph node procedure, although this is rare.

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