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Sentinel Node Procedure

By: Pamela H. Craig, M.D., Ph.D., F.A.C.S. Surgeon, The Breast Center

The sentinel node procedure is a new technique used by breast surgical specialists to find out whether there are breast cancer cells in the lymph nodes in your axilla.

Traditionally, when a woman had a mastectomy all, or almost all, of the tissue in the axilla was removed along with the breast. This tissue consists of fat, lymph nodes, lymph and blood vessels, and some nerves. Removal of this tissue either as part of a mastectomy or through a separate incision in the axilla is called an axillary dissection. Surgeons used to think that the best way to treat breast cancer was to remove the entire breast and any cancer cells that might be in the axillary tissue. During the last 20 years, we now understand that removing the axilla does not prevent the spread of breast cancer. At about this same time, we learned that we can treat breast cancer with breast conservation (removing only the cancer from the breast, followed by radiation to the remaining breast tissue). And we found that we could make a separate incision in the axilla and remove some, but not all, of the tissue there. We also learned that those women who do have cancer cells in their axilla benefit from additional treatment with chemotherapy or hormone therapy. Also, in those women who have some cancer cells in their nodes, it sometimes helps us to know how many nodes have these cells so that we can plan additional treatment.

The majority of women with breast cancer do not have cancer cells in their axillary nodes (the chances depend a lot on the size of the tumor). When a study was done to see if leaving the axillary nodes affected women's survival, we found no difference in outcome after following these women for 15 years. So breast cancer specialists are asking the question "why should we take out the axillary tissue in the majority of women if it does not help them?" Furthermore, removing all this axillary tissue can cause serious problems in some women: chronic pain, soreness, tingling, numbness, and lymphedema (chronic swelling of the arm).

Patients with DCIS (non-invasive breast cancer or ductal carcinoma in situ) and many patients with small breast cancers (less than 1/4 to 1/2 inch in diameter) probably don't benefit from an axillary dissection because the chance of having any cancer cells there is less than 1 in 10. Some oncologists think that for larger size cancers of the breast, the patient should receive chemotherapy anyway so there is no need to remove the axillary contents. Other oncologists think that for larger tumors, we should remove the axillary nodes so that we can find out exactly how many nodes are involved and use special chemotherapy for those patients who have a large number of positive nodes.

If all this sounds confusing and controversial, it is. The sentinel node procedure helps to untangle this controversy. The sentinel node refers to the "node on watch." We already know that this node is the first node to receive cancer cells and that if this node is positive, there may be other positive nodes upstream. The cancer cells don't "skip" and go to higher nodes. If this node is negative, all the upstream nodes are negative 99 out of 100 times.

The way it works is that your surgeon will inject the tissue around the tumor in your breast with a labeling substance, a blue dye or a minute amount of radioactively labeled tracer substance (the same tracer which will be used for your bone or liver scan). These substances travel to the sentinel node. Through a small incision in the axilla the surgeon can pick out the node (sometimes there are 2 or 3) that turns blue with the dye and/or emits a radioactive particle which is then detected with a probe like a Geiger counter. The blue dye and the radioactive tracer are used because the "sentinel node" is not always easy to find. The pathologist then very carefully and meticulously examines all the cells in that sentinel node under a microscope. They used to have to look through 10 or 20 or even more of these little nodes. Lymph nodes can be about the size of peas or beans, sometimes very tiny, the size of a grain of rice. Because of the technical difficulties in finding cancer cells in lymph nodes, the pathologist would not be able to find cancer cells in lymph nodes 10 to 20% of the time. The sentinel node procedure therefore has the added advantage of being more accurate and telling the oncologist even more clearly the status of your lymph nodes. If the sentinel node is "negative" for cancer cells, we know that accurately predicts that the rest of the nodes are negative. And you do not have to have an extensive surgical procedure, which could have some side effects. If that node is positive, we will discuss with you if you should undergo a complete axillary dissection to remove the rest of the nodes. In some cases, positive may mean just a few cells, or in other cases, it may mean the whole node has cancer cells in it. The treatment may be different in either case.

What are the pros and cons of the sentinel node procedure? If you do not need to have an axillary dissection, with the sentinel node technique you are spared an unnecessary axillary dissection and the potential complications of swelling and nerve irritation. The blue dye will turn your urine green for about 24 hours. Rarely, there may be a slight bluish discoloration of the tissue in the breast. This usually goes away. The radioactive tracer is used in tiny amounts (less than a bone scan) and it disappears from your system in 24-48 hours. If the sentinel node is positive, you may need a second surgical procedure to remove your remaining nodes.

An axillary node dissection, which removes much of the lymph node-bearing tissue under the arm, is still considered the "standard approach." But many centers are using the sentinel node technique for women with early breast cancer because it offers a reasonable alternative to aggressive unnecessary surgery much as removing a breast tumor alone (lumpectomy) has become an attractive alternative to removing the entire breast (mastectomy).

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