Sentinel Node Identification in Breast Cancer Treatment

A vital step

By Krishnansu S. Tewari, MD, FACOG, FACS

The sentinel node procedure in breast cancer was developed during the 1990s. With this procedure the surgeon attempts to pinpoint the first few lymph nodes into which the cancer in the breast drains. These first few nodes are guardian node(s), and for this reason they are referred to as sentinels. The sentinel nodes are significant in breast cancer treatment because they are the first place that breast cancer is likely to spread. Because the cancer cells don’t “skip” and go to higher nodes, if the sentinel(s) is/are negative, all the upstream nodes are negative 99 out of 100 times.

The sentinel node in breast cancer is usually located in the axillary nodes, under the arm. Identification of the sentinel lymph node also allows for conservative surgery because if that lymph node is found to be cancer-free, then all of the lymph nodes in that axilla do not need to be removed. Avoidance of a full axillary surgery has significant benefits for patients including less surgical pain, less scarring, and perhaps most importantly, less swelling in the arm on the side of the surgery (lymphedema).

To find the sentinel node(s), a radioactive tracer and a blue dye are usually injected into the area around the tumor before the lumpectomy is performed. The tracer and the dye travel along the same path to the lymph nodes that the cancer cells would take. After making an incision in the axilla (separate from the incision used for the lumpectomy) the surgeon can identify the sentinel node(s) by their blue color and by using a hand-held Geiger counter to detect the radioactive node(s). Once identified the sentinel(s) are sent to the pathologist for microscopic evaluation. If cancer cells are found in the sentinel(s), then the surgeon will often proceed with a full dissection of that axilla. If the sentinel(s) is/are negative, as discussed above, no further surgery in the axilla is required. The blue dye may cause a slight bluish discoloration in the breast, but this will fade. A patient’s urine may also be green for about 24 hours. The radioactive tracer is used in very small amounts and disappears from the body in 24-48 hours.

Though results of important clinical trials involving lymph node identification are expected in 2009, it appears from the existing medical literature that sentinel lymph node identification using blue dye plus radioactive tracer is safe in regards to both side effects and cancer-related survival.