Sentinel node biopsy is a relatively new way of pinpointing the first few lymph nodes into which a tumor drains (called the "sentinel" node). This helps us remove only those nodes of the lymphatic system most likely to contain cancer cells. The sentinel nodes are the first place that cancer is likely to spread. Sentinel node biopsy is most commonly associated with staging breast cancer; however, the procedure is also commonly used to stage malignant melanoma. Sentinel node biopsy may also be called sentinel lymph node biopsy or sentinel lymph node dissection.
In breast cancer, the sentinel node is usually located in the axillary nodes, under the arm. In a small percentage of cases, the sentinel node is found somewhere else in the lymphatic system of the breast. If the sentinel node is positive there may be other positive lymph nodes upstream. If it is negative, it is highly likely that all of the upstream nodes are negative.
LYMPH NODE DISECTION:
If breast cancer has spread beyond the lining of the breast duct, and is picked up by the blood vessels or lymph vessels, then it can potentially spread elsewhere in the body, or “metastasize.” Lymph vesselsare small channels that drain all the tissues of the body. Lymphvessels drain excess fluid back into circulation. As lymph fluid drains back into the circulation, it goes through lymph nodes. Lymph nodes are collections of lymph tissue that have a high concentration of white blood cells, the cells that fight infection and cancer. The lymph vessels of the breast drain into the lymph nodes in the axillaand sometimes into the lymph nodes along the sternum, and above the clavicle.
The first node that the fluid passes through in a group of lymph nodes is called the sentinel lymph node. The term sentinel is derived from the French word sentinelle, which means "to guard over" or"vigilance." Thus, the sentinel lymph node is the protective node that acts as the first filter of harmful materials.
During a sentinel lymph node biopsy, the surgeon usually removes one to five sentinel lymph nodes and sends those nodes for examination by a pathologist to determine if cancer cells have spread to them. If cancer cells are found in these lymph nodes, it means that the cancer might be metastasizing. Therefore, a sentinel node biopsy is an important tool in determining what further treatment is necessary for the cancer as well as determining the patient's prognosis. Sentinel node biopsy has been in use for over 10 years. The traditional procedure for staging breast cancer used to be axillary lymph node dissection (ALND), which involves removing most (usually 10-30) of the lymph nodes in the armpit closest to the breast tumor.
SENTINEL NODES
AXILLARY LYMPH NODE DISSECTION:
Traditionally, with invasive breast cancer, an axillary lymph node dissection (ALND) is recommended in order to see if the cancer has spread to the lymph nodes underneath the arm. During an axillary lymph node dissection, the surgeon makes an incision underneath your arm, and removes the bulk of the lymph node tissue that drains from the breast. The lymph node tissue is then sent to the laboratory, and a pathologist determines if any of them contain cancer. On average, approximately 10 to 30 lymph nodes are removed with this operation. An axillary lymph node dissection usually requires an overnight stay in the hospital. Since the remaining tissues underneath the arm tend to “leak” some lymph fluid when the lymph nodes are removed, a drain is left in place for the first 2-3 weeks after the operation until the area heals. The drain is a flexible plastic tube that exits the skin, and is connected to a plastic collection bulb. When the drainage diminishes to a certain amount, the drain is removed. After discharge the patient requires physical therapy to maintain strength and flexibility in the shoulder while this area heals. Approximately 10-20% of the patients who undergo an axillary lymph node dissection experience chronic problems related to the dissection such as arm swelling (lymphedema), or pain or discomfort in the area of the dissection. Almost all women will have some residual numbness under the inside of the arm.
THE BENEFIT OF ALND:
The single benefit of ALND is that all of the lymph nodes can be examined for the presence of cancer cells, and we can use those findings to make a reliable determination of whether the cancer is spreading.
THE DISADVANTAGES OF ALND:
The drawbacks of ALND are that the procedure is associated with postsurgical complications such as movement problems in the shoulder, wound infection, nerve damage, and lymphedema. Lymphedema is swelling, most often in the arms and legs, caused by accumulation of lymphatic fluid (fluid that helps fight infection and disease). Only 10%-20% of women who undergo an ALND develop lymphedema, but it can be a serious, untreatable condition that involves painful and chronic swelling of the arm.
SENTINEL LYMPH NODE BIOPSY:
Experience has shown us that the lymph ducts of the breast usually drain to one lymph node first, before draining through the rest of the lymph nodes underneath the arm. That first lymph node is called the sentinel lymph node. That is the lymph node that helps sound the warning that the cancer has spread. Lymph node mapping helps identify that lymph node, and a sentinel lymph node biopsy removes only that lymph node.
The sentinel lymph node is identified in one of two ways, either by a weak radioactive dye (technetium-labeled sulfur colloid) that can be measured by a hand held probe, or by a blue dye (isosulfan blue) that stains the lymph tissue a bright blue so it can be seen. Most breast cancer surgeons use a combination of both dyes.
PROCEDURE:
The morning of the operation, the patient goes to nuclear medicine the injection of the radioactive dye used for the procedure. The injections are done into the area of the breast where the tumor is (if a NL has been performed to localize the tumor this wire can be used to direct the injections), and around the nipple areolar complex of the breast. The patient returns to the nuclear medicine department a few hours later, and a lymphoscintigram will be taken which shows the pathways the dye takes as it leaves the breast. This helps guide the surgeon in identifying the sentinel lymph node.
At the beginning of the operation, the surgeon injects the blue dye. The surgeon then makes an incision underneath your arm in the area of the axillary lymph tissue. A hand-held sterile probe measures areas that have the radioactive dye. The lymph nodes that have taken up theradioactive dye, or are stained with the blue dye, are removed.
Usually one to three nodes are removed. These nodes are sent to pathology, to determine if the sentinel node contains cancer. The incision is closed. There is no need for a drain, there is no need for physical therapy exercises, and the patient can usually go home from the hospital that day. The sentinel lymph node biopsy can be done in combination with a lumpectomy, or a mastectomy. The procedure is successful in >90% of those patients whom we think are good candidates for the procedure. If the procedure is unsuccessful in identifying the sentinel node, a full axillary dissection must be done.
ADVANTAGES:
The advantages to the sentinel lymph node procedure are many. There is no need to stay overnight in the hospital. There is no need for a drain, or physical therapy exercises. The recuperation from the procedure is faster. The patient is typically doing her regular activities within a few days, and the incision is well healed within a few weeks. A sentinel lymph node biopsy can lead to a more accurate assessment of whether the cancer has spread to the lymph nodes. In a traditional axillary dissection, the pathologist receives 10-30 lymph nodes or more; there is no way of telling which one is the sentinel lymph node. So the pathologist makes one cut in each lymph node and looks for cancer. When the pathologist receives only one, or a few, lymph nodes from a sentinel lymph node procedure, he or she can make many cuts through that lymph node to look for cancer. A negative sentinel lymph node(s) indicates a >95% chance that the remaining lymph nodes in the axilla are also cancer free. Therefore, there is no need to undergo a full axillary lymph node dissection, or to risk the long
term complications and side effects from an axillary dissection.
CONTRAINDICATIONS FOR SENTINEL NODE BIOPSY:
Not all women are good candidates for sentinel node biopsy. A woman with any of the following may be a poor candidate for the procedure:
- Lymph nodes that are palpable (can be felt through the skin) and hard (in this situation a fine needle aspirate of the lymph node can help determine if it is cancerous or not)
- cancer already identified in the lymph nodes (by FNA)
Prior mastectomy.
In addition, the following factors are associated with an increased risk of complications involving most surgeries (but none are specific contraindications to sentinel lymph node biopsy):
Poor general health
Long-term illness
Obesity
Advanced age
Smoking
Conditions that affect the blood
Using certain medications or
dietary supplements
SUMMARY:
Invasive breast cancer can spread through the lymph ducts and blood vessels to other areas of the body. The sentinel lymph node is the first lymphnode that the lymph ducts drain into. Whether or not the cancer has spread to the sentinel lymph node indicates whether the cancer has started to spread beyond the breast to invade the rest of ourpatient’s body. Sentinel lymph node biopsy identifies this critical lymph node, and allows only this lymph node to be removed.
Removing only the sentinel lymph node can allow our breast cancer patients to avoid many of the complications and side effects associated with a traditional axillary lymph node dissection.
Patients with invasive breast cancer deserve not only every fighting chance to live but also, if at all possible, the right to live comfortably, with dignity and complication free.
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