What is a sentinel lymph node biopsy?

A sentinel lymph node biopsy is a technique that allows doctors to identify which lymph nodes in the underarm are the first ones to get tumor drainage from the breast. Using this technique, doctors can remove only the affected lymph nodes. Usually it’s about two lymph nodes, but occasionally it’s three or four. This minimizes the chance of complications from the surgery, such as lymphedema, while still providing the necessary information. This technique is basically the standard of care for early breast cancer, and it’s a very effective way to assess the status of the lymph nodes without subjecting the woman to a high risk of complications from the surgery.
Sentinel lymph node biopsy

Sentinel lymph node biopsy (SLNB) is a way of learning if cancer has spread to lymph nodes without removing all of them.

In this procedure the surgeon finds and removes the first lymph node(s) (sentinel node or nodes) to which a tumor drains, and the one(s) most likely to contain cancer cells if they have started to spread. To do this, the surgeon injects a radioactive substance and/or a blue dye into the tumor or the area around it. Lymphatic vessels will carry these substances into the sentinel node(s). The doctor can use a special device to detect the radioactivity in the nodes that the radioactive substance flows into or can look for lymph nodes that have turned blue. These are separate ways to find the sentinel node, but are often done together as a double check. The doctor then cuts the skin over the area and removes the nodes. These nodes (often 2 or 3) are then looked at closely by the pathologist. (Because fewer nodes are removed than in an axillary lymph node dissection, each one can be looked at more closely for any cancer).

If there is no cancer in the sentinel node(s), it's very unlikely that the cancer has spread to other lymph nodes, so no further lymph node surgery is needed. The patient can avoid the potential side effects of a full axillary lymph node dissection.

If the sentinel node(s) has cancer, the surgeon will do a full axillary lymph node dissection to see how many other lymph nodes are involved. The lymph node can sometimes be checked for cancer during surgery. If cancer is found in the sentinel lymph node, the surgeon may go on to remove more lymph nodes or even do a full axillary dissection. If no cancer cells are seen in the lymph node at the time of the surgery, or if the sentinel node is not checked at the time of the surgery, the lymph node(s) will be examined in greater detail over the next several days. If cancer is found in the lymph node, the surgeon may recommend a full axillary lymph node dissection at a later time.

Sentinel lymph node biopsy requires a great deal of skill. It should be done only by a surgical team known to have experience with this technique. If you are thinking about having this type of biopsy, ask your health care team if they do them regularly.
Your surgeon may recommend a sentinel lymph node biopsy. The 'sentinel' node is the first lymph node (or nodes) in your underarm that receives lymph fluid from the area in your breast where the cancer is located. These nodes are identified by injecting dye into the breast before surgery. An incision is made under the arm to remove the sentinel nodes draining the breast. These nodes may or may not be checked by pathology when you are in the operating room. 
Dede Bonner
Health Education
If your surgeon is planning to remove any or all of your lymph nodes, ask this important follow-up question: “Is a sentinel node biopsy an option in my case?” A sentinel node biopsy is a less-invasive way to check for cancer that may have spread to the lymph nodes. Following injections with a tiny amount of radioactive liquid and dye into the area with cancer, the surgeon removes only the sentinel nodes so that they can be tested to see whether they contain cancer cells. The results of research trials suggest that sentinel node biopsy is as effective at detecting cancer cells in the lymph nodes as lymph node sampling or clearance.
The 10 Best Questions for Surviving Breast Cancer: The Script You Need to Take Control of Your Health

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The 10 Best Questions for Surviving Breast Cancer: The Script You Need to Take Control of Your Health

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The sentinel lymph node biopsy technique was developed that allowed breast cancer staging without removal of all of the lymph nodes in the armpit area. If the sentinel nodes contained cancer only then would a full axillary dissection (removal) be performed in which the rest of the lymph nodes would be removed.

A sentinel lymph node biopsy is an outpatient surgical biopsy (removal with analysis under a microscope) of lymph nodes from under the arm on the same side as the cancer. This type of biopsy limits the extent of surgery in the armpit (axilla) by only removing the lymph nodes that are most likely to have tumor. If the sentinel lymph nodes do not have tumor in them, then the rest are probably tumor free also. In a sense, these sentinel nodes are “on guard” for the rest of the lymph nodes, hence the name “sentinel” nodes.
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