How is a sentinel lymph node biopsy performed?

During a sentinel lymph node biopsy, doctors inject a tracer substance into the breast. They can use a blue dye called lymphazurin or isosulfan blue or a radiolabeled sulfur colloid, or both. It's most effective is when both substances are used. After the tracer substance is injected into the breast, it gets taken up by the lymphatic vessels. It then travels to the lymph nodes in the underarm. The tracer substance travels to the same nodes that the cancer would spread to first. These nodes are called the sentinel nodes.

Then, the surgeon makes a small incision in the underarm using either a visual aid or a little probe that picks up radioactive counts. The surgeon can then find the sentinel nodes and remove only those lymph nodes for biopsy.
The sentinel node is thought to be the first lymph nodes or group of lymph nodes in your armpit that receives lymph fluid from the area where the cancer is located in the breast. Your surgeon may pinpoint the located of the sentinel lymph nodes in two ways:

- injecting a harmless radioactive substance into your breast where the tumor is before the surgical procedure.
- injection of a small amount of blue vegetable dye into your breast where the tumor is during the surgical procedure.

The surgeon then removes the sentinel lymph nodes that have become highlighted with the blue dye or radioactive fluid. The lymph nodes are sent to the pathology room for immediate examination under a microscope while you are still in the operating room. If the sentinel node is free of cancer cells, your surgery is complete. If cancer cells are detected, your surgeon will remove several more lymph nodes.

Sometimes, additional examination of breast tissue or sentinel lymph nodes reveals the presence of cancer cells after your surgery. In this situation, your surgeon may recommend more surgery to remove more lymph nodes for analysis.
The sentinel node is identified by utilizing a radioactive tracer, a blue dye, or both modalities. If your surgeon utilizes the radioactive tracer, on the day of surgery, you will receive a small amount of radioactive tracer injected around the tumor or under the nipple. A scan will be done to trace the flow of the radioisotope through the lymph system to find the location of the sentinel node(s). This part of the procedure takes 60 to 90 minutes.

You will then be taken to the operating room, where the surgeon injects a blue dye into the area around the tumor or under the nipple. This is done after you receive general anesthesia. The blue dye flows through the lymphatic system and into the sentinel lymph node(s), coloring them blue. The surgeon has a small device, called a gamma probe, that can be used like a Geiger counter to look at the activity of the radioisotope in the various lymph nodes that drain the breast. This probe helps the surgeon find the location of the sentinel lymph node(s).

Through a small incision under the arm, the surgeon identifies any lymph nodes that are blue-stained, radioactive or palpably abnormal, and these nodes are removed. These are sent to the Pathology lab for an immediate reading (frozen section). If the node(s) have tumor in them, an axillary node dissection is performed. If the sentinel node(s) are clean, no further axillary surgery is performed. There is a 5% chance that the sentinel node(s) will be clean on the frozen section but may contain small amounts of tumor when studied more extensively on the permanent sections. If this happens, you will need to return to the operating room for a completion axillary dissection.

Remember that the radioisotope dye and lymph node scan does not tell you that the cancer has spread. They only mark the first node(s) that the cancer cells might have spread to so that the surgeon can remove them to be tested. Only the pathologist, by looking under the microscope, can tell whether cancer cells have spread to the lymph nodes.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.