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Sentinel Node Biopsy (cont.)

Preparation

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. 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 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. This can be injected either around the tumor or underneath the nipple/areola. Both techniques are used and both are very successful.
  • 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 (making them look like they might be nauseated) 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.

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