Sentinel Node Biopsy

What Facts Should I Know about a Sentinel Node Biopsy?

What is the medical definition of a sentinel node biopsy?

  • Sentinel node biopsy is a surgical procedure that doctors use to stage (determine the extent of spread of) certain types of cancer in patients who have been recently diagnosed with cancer. Sentinel node biopsy is most commonly associated with staging breast cancer; however, the procedure is also commonly used to stage malignant melanoma (a type of skin cancer). Sentinel node biopsy may also be called sentinel lymph node biopsy or sentinel lymph node dissection.
  • Lymph nodes are pea-sized structures that filter tissue fluids called lymph or lymphatic fluids that circulate through the body. The lymph nodes collect foreign materials such as cancer cells, bacteria, and viruses from these fluids. White blood cells, which are components of the immune system, attack the collected foreign material in the lymph nodes. Malignant (cancerous) tumors, such as breast cancer, may grow and spread enough that the lymph and blood vessels that run through the breast begin to circulate the cancer's cells through the body, and they may begin to grow in other locations as a result. Most cancerous breast tumors drain to the group of lymph nodes in the underarm closest to the growing tumor.
  • 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.

How is a sentinel lymph node biopsy performed?

  • During a sentinel lymph node biopsy, the surgeon usually removes one to five sentinel lymph nodes (from an underarm if breast cancer is involved) 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 (spreading through the body). Therefore, a sentinel node biopsy is an important tool for doctors to use in determining what further treatment is necessary for the cancer as well as determining the patient's prognosis.

Why is a lymph node biopsy done?

  • Sentinel node biopsy has been in use for almost 20 years. The traditional procedure for staging breast cancer used to be a surgery called axillary lymph node dissection (ALND), which involves removing most (usually 10-30) of the lymph nodes in the armpit closest to the breast tumor. The benefit of ALND is that all of the lymph nodes can be examined for the presence of cancer cells, and the doctor can use those findings to make a reliable determination of whether the cancer is spreading.
  • The drawback of ALND is 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 an accumulation of lymphatic fluid (fluid that helps fight infection and disease) that cannot drain once the lymph nodes are removed. Only some women who undergo an ALND develop lymphedema, but it can be a serious, untreatable condition that involves painful and chronic (long-term) swelling of the arm.

How long does it take to recover from lymph node removal?

  • By design a less-invasive method to stage breast cancer than ALND, sentinel node biopsy is associated with fewer complications that may develop after the procedure. Instead of all of the lymph nodes being removed, sentinel node biopsy involves removing an average of two to three lymph nodes. Compared to ALND, sentinel node biopsy usually takes less time to perform, is less painful, requires a much smaller incision, and is associated with a shorter recovery period. The main argument in support of sentinel node biopsy is that if no cancer has spread to the sentinel lymph nodes, removal of the remaining lymph nodes is not warranted. Doing so would only increase the risk of postsurgical complications without providing further benefits.

Why dye is used in a sentinel lymph node biopsy?

  • In addition, the accuracy involved with a sentinel node biopsy is comparable or better to those of ALND. Surgeons who are accustomed to the procedure can identify the sentinel lymph node in most patients. They can also accurately determine if the cancer is spreading in most patients. A special dye or a radioactive tracer is used to help identify the sentinel nodes. The false-negative rate (percentage of cases in which no cancer cells are found in the sentinel lymph node, but are present in "downstream" nodes) is less than 5%.
  • The way the pathologist processes and evaluates sentinel lymph nodes is different from how they would evaluate the nodes retrieved in an axillary dissection. Specifically, the pathologist looks at many more portions of the sentinel node and may perform special studies to enhance the ability to identify cancer cells on those nodes. This provides a more in-depth look at each sentinel node.

What does a sentinel node biopsy procedure look like? (pictures)

Sentinel lymph node biopsy in patients with melanoma. Intraoperative left axillary sentinel lymph node seen after uptake with blue dye.
Sentinel lymph node biopsy in patients with melanoma. Intraoperative left axillary sentinel lymph node seen after uptake with blue dye.

After further dissection, the blue node is easily identifiable. This node was removed and contained a large amount of radioactive tracer.
After further dissection, the blue node is easily identifiable. This node was removed and contained a large amount of radioactive tracer.

Who Is Not a Good Candidate 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)
  • The only absolute contraindications are
    • cancer already identified in the lymph nodes (by FNA) and
    • 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

How Do You Prepare for a Sentinel Node Biopsy?

In preparation for a sentinel node biopsy, the patient usually undergoes tests of the blood and urine and a mammogram (an imaging test of the breast that helps determine the location of the tumor) if the procedure is being done for breast cancer diagnosis.

The doctor may advise the patient to stop taking medications such as aspirin, antiinflammatory drugs, anticoagulants (drugs that thin the blood), and dietary supplements (such as ginkgo biloba) for a few days prior to the procedure. The doctor may also recommend that the patient either eat lightly or avoid food and beverages altogether for a certain number of hours (usually eight to 12) prior to surgery.

To prepare for the surgery, the doctor first needs to determine which of the lymph nodes is the sentinel lymph node. The doctor may use one or both of the following methods to locate the sentinel lymph node:

  • Radioactive tracer injection: This involves an injection of a small dose of technetium-99, a low-level radioactive tracer. The radiation exposure from technetium-99 is less than that obtained from a standard X-ray. The doctor injects this tracer into the breast, near the tumor or underneath the nipple/areola. Both techniques are used and both are very successful. The tracer then mixes with the fluids that travel to the lymph nodes. Later, during surgery, the doctor uses a Geiger counter (a small device that measures radiation levels) to determine which lymph node(s) contains the radiation. This pinpoints which lymph node is the sentinel lymph node. Depending on the preference of the doctor, this may be injected 20 minutes to eight hours before the surgery.
  • Blue dye injection: For visual confirmation of the sentinel lymph node, the doctor usually injects a blue dye called isosulfan blue (Lymphazurin) near the tumor. This mixes with the fluids that travel to the lymph nodes. When the doctor makes the incision after injecting the dye, the sentinel lymph is colored blue. The doctor may inject this a few minutes before the actual surgery or during the surgery. This dye turns the urine green for about 24 hours and occasionally creates a temporary bluish stain on the breast tissue. In light-skinned women, it also makes their skin appear a bit green for a few hours after surgery. This dye is no longer available in many centers.

The success rate for locating the sentinel lymph node with an injection of blue dye alone is 82%. The radioactive tracer injection is associated with a 94% success rate. The combination of both carries a 98% success rate, although an experienced surgeon will typically find a node with a single agent in >95% of cases.

Often, a sentinel node biopsy is performed during a lumpectomy or a mastectomy. A lumpectomy is a surgical procedure that involves removing a breast tumor surrounded by a rim of normal tissue. A mastectomy is a surgical procedure that involves removing the whole breast. If the doctor performs one of these other procedures in addition to the sentinel node biopsy, the woman usually receives general anesthesia to prevent pain and awareness during surgery. Occasionally, the woman may receive only local anesthesia, which involves numbing only the area involved in the surgery.

What Happens During the Sentinel Node Biopsy Procedure?

Sentinel node biopsy is usually performed at the same time that a lumpectomy is performed. If this is the case, the sentinel node biopsy is usually performed first.

Depending on the preference of the doctor, the blue dye or radioactive tracer may be injected after the woman has received anesthesia. The surgeon then uses a handheld Geiger counter to determine the exact location of the sentinel lymph node and makes a small incision over that point. If the patient has been injected with blue dye, the sentinel lymph node is colored blue. This provides the surgeon with visual confirmation of the sentinel node.

The surgeon then removes an average of two to three sentinel lymph nodes for examination under a microscope. Depending on the surgeon's practice and suspicion, a pathologist may do a quick test after freezing the material (known as a frozen section) to examine these nodes for cancer while the surgeon performs the lumpectomy or the mastectomy. If cancer cells are found in the sentinel lymph node, either at the time of surgery or when the final report from the pathologist is available, the surgeon then performs an axillary lymph node dissection.

A sentinel node biopsy typically takes about 45 minutes to perform. If a lumpectomy is also being performed, an extra 30-45 minutes are usually added to the total surgery time.

For melanoma, the basics of the procedure are the same. However, not all patients with melanoma require a sentinel lymph node biopsy. If lymph nodes are palpable during a physical examination a sentinel lymph node biopsy is mandatory. For most patients a melanoma less than 1 mm thick does not require a sentinel lymph node biopsy, unless ulceration of the melanoma is present. For tumors 1-4 mm thick, the incidence of lymph node spread increases as the thickness increases. Therefore, sentinel lymph node biopsy of the draining basins are carried out. If there is a positive sentinel lymph node, a complete regional lymphadenectomy (removal of all of the draining lymph nodes) is performed. This is standard of care. However, this procedure has not been demonstrated to improve survival of patients with melanoma.

For patients with deep melanoma, sentinel lymph node biopsy alone is sufficient due to the severe side effects of lymphadenectomy. The sentinel node biopsy is helpful, however, in guiding diagnostic, prognostic and therapeutic decision making.

Persons with melanoma, who have a positive sentinel lymph node, may benefit from additional therapy such as radiation, interferon, interleukin, or, based upon new information, the drugs ipilimumab (Yervoy), nivolumab (Opdivo), or pembrolizumab (Keytruda) may be considered.

After the Sentinel Node Biopsy Procedure

Patients who undergo a sentinel lymph node biopsy are taken to the recovery room following the procedure. Most are released from the hospital the same day. The radioactive tracer safely dissipates, mostly in the urine, within 24-48 hours.

The incision usually heals within a few weeks. Regular activities can be performed within a few days.

What Are the Next Steps after Sentinel Node Biopsy?

If the sentinel lymph node was not examined during surgery, the pathologist tests it for cancer cells soon afterward. The doctor addresses the findings of the examination during a follow-up visit.

If the pathologist finds cancer cells in the sentinel lymph node, the patient usually undergoes a follow-up surgery to undergo an axillary lymph node dissection. This involves removing and testing the remaining lymph nodes in the area of the original biopsy for cancer cells. Depending on the findings and the choice of primary breast surgery (lumpectomy or mastectomy), women who undergo surgery to stage breast cancer or to remove breast tumors may also be treated with chemotherapy, hormonal therapy or radiation therapy to kill any remaining cancer cells.

What Are the Risks of a Sentinel Node Biopsy?

Sentinel node biopsy is a procedure that is designed to minimize risks. It is a useful tool for staging breast and other cancers and determining what further treatment is appropriate to offer the patient to provide the highest possible chance of survival. Sentinel node biopsy is also an emerging procedure designed to minimize the risks associated with an axillary lymph node dissection. The most significant risk is that a sentinel node biopsy results in a determination that cancer cells are not metastasizing in the body when, in fact, they really are. This is called a false-negative result. This is a reason that a woman should ensure that her surgeon has performed the procedure several times with accurate results before she undergoes the surgery.

Rarely, a patient can have an allergic reaction to the blue dye. The most mild and most common type of allergic reaction is hives. Hives are usually seen within 24 hours of the dye injection. A very rare patient will have a severe allergic reaction, but this usually happens within minutes of the injection of the dye. Other possible risks of a sentinel node biopsy may occur and are usually mild in severity. These include the following:

  • Pain, discomfort, or fluid collection causing a lump, or numbness (usually short-lived) in the area of the incision
  • Bluish discoloration of the breast tissue (usually temporary, but can be permanent) following injection of the blue dye
  • Drowsiness

The following are possible complications following most surgical procedures:

What Do the Results of Sentinel Node Biopsy Mean?

Surgeons who are experts at sentinel node biopsy can identify the sentinel lymph node in 85%-98% of patients. They can also accurately determine if the cancer is spreading in 95% of patients. The false-negative rate is less than 5%.

When to Seek Medical Care for Sentinel Node Biopsy Complications

Following surgery, the patient should contact her doctor if any of the following symptoms develop:

  • Signs of infection (for example, redness, swelling) in the incision area
  • Fever or chills
  • Increasing pain
  • Excessive bleeding or discharge from the incision wound
  • Chest pain
  • Cough or shortness of breath
  • Severe vomiting or nausea
  • New, unexplained symptoms

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Sentinel Node Biopsy for Breast Cancer: What to Expect at Home

After a sentinel node biopsy, many women have no side effects. Some women have pain or bruising at the cut (incision) and feel tired. Your breast and underarm area may be slightly swollen. This may last a few days. You should feel close to normal in a few days. The incision the doctor made usually heals in about 2 weeks. The scar usually fades with time.

Medically reviewed by Jay B. Zatzkin, MD; American Board of Internal Medicine with subspecialty in Medical Oncology


"Diagnosis, staging and the role of sentinel lymph node biopsy in the nodal evaluation of breast cancer"