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Sentinel Node (Lymphoscintigraphy)
It used to be that doctors had to make a reasonable guess about which lymph nodes were the sentinel lymph nodes in patients with breast or skin cancer (melanoma). These are the nodes that serve as a kind of catch basin for drainage of the lymph system and are the nodes most likely to harbor cancer cells if the disease has spread. Before scintigraphy, a relatively new technique in nuclear medicine, surgeons would make an educated guess about which nodes were the sentinel nodes and then remove all of the nodes in that particular drainage pathway or region.
With scintigraphy your surgeon can actually see the drainage pathway more clearly and pinpoint precisely which nodes are the sentinel lymph nodes. Although the procedure is still surgical since tissue is being removed, scintigraphy provides enough precision that it’s almost as if the surgeon is “picking” out these nodes that can be as small as a grain of rice or as large as a bean.
You don’t have to do anything special to prepare for this test.
You will lie on a table for this procedure. A topical anesthetic such as lidocaine is spread over the injection area. Then, your doctor will inject a small amount of radioactive isotope in up to four sites around the areola for breast cancer patients.
If you have melanoma the injections will be made near the site of the tumor. Your doctor may mark on your skin to help the surgeon find the nodes. Then, in the operating room, your surgeon will use a special probe along with the pictures to identify and remove the sentinel nodes. The nodes will be sent to pathology to determine the presence or absence of cancer.
When you are having the lymphoscintigraphy you will see a gamma camera that follows the tracer materials through the lymph system to the sentinel lymph nodes. Afterward when the sentinel nodes are removed the surgeon will use a hand-held probe that looks like a portable Geiger counter moving over the cancer site and surrounding lymph tissue.
There may be a slight sting with each injection. It is very important to remain still during the injection and withdrawal of the needle. You will have to stay in one position for about two minutes or less.
In some patients whose sentinel lymph nodes are cancer negative this procedure may eliminate the need for surgical removal of the whole lymph area. When the sentinel nodes can be pinpointed so accurately there is a much smaller incision to remove the lymph nodes. Because of its accuracy, the procedure also may reduce the number of lymph nodes that need to be removed. The test provides more accurate information about whether the cancer has spread.
You will be exposed to less radiation than if you had a chest X-ray.
The radiologist and surgeon will confer with your doctor who will call you about the results of the biopsy.
There may be some discoloring of your skin from the blue dye used in the procedure and your urine may be green for a day or two. These are effects of the surgical procedure not the nuclear medicine study.