Sentinel Lymph Node Biopsy (SLNB)

In a sentinel lymph node biopsy (SLNB), the surgeon finds and removes the first lymph node(s) to drain fluid from the breast. This has been shown in numerous studies to be the lymph node(s) to which a tumor has spread if it indeed has spread.

To do this, the surgeon injects a radioactive substance and/or a blue dye into the tumor, the area around it, or the area around the nipple. Lymphatic vessels will carry these substances along the same path that the cancer would take if it travels to the lymph nodes. The first lymph node(s) the dye or radioactive substance travels to will be the sentinel node(s). These sentinel nodes are the nodes that are removed at surgery through a small incision in the armpit.

The removed lymph nodes (on average 2-5 nodes) are then checked closely for cancer cells by a pathologist under a microscope. Sometimes, this is done during the surgery. Because there is a chance that other lymph nodes in the same area will also have cancer if cancer is found in the sentinel lymph node(s), the surgeon may go ahead with a full axillary lymph node dissection (ALND) to remove more lymph nodes while you are still on the operating table (this is most commonly done if undergoing a mastectomy or had chemotherapy before surgery). If they are not checked by a pathologist during the surgery, they will be examined more closely over the next several days.

If cancer is found in the sentinel node(s) later, the surgeon may recommend a full ALND at a later time to check more nodes for cancer. Studies have shown however that in many cases it may be safe to leave the rest of the lymph nodes behind. This is based on certain factors, such as the size of the breast cancer, what type of surgery is used to remove the tumor, and what treatment is planned after surgery.

Based on the studies that have looked at this, skipping the ALND may be an option for:

  • Women with tumors 5 cm (2 inches) or smaller who have fewer than 3 positive sentinel lymph nodes and are having breast-conserving surgery followed by radiation.
  • Women who have had mastectomy and will also have radiation.

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 will be needed.

SLNB is often considered for women with early-stage breast cancer and is typically not an option for women with inflammatory breast cancer.

Although SLNB has become a common procedure, it requires a great deal of skill. It should be done only by a surgeon who has experience with this technique. Dr. Hamilton and Dr. O’Leary have extensive experience with this technique, including women undergoing SLNB after neoadjuvant chemotherapy (chemotherapy given before surgery).