Breast cancer surgery: the importance of lymph node dissection

Breast cancer surgery involves more than just removing tumours. Surgeons also need to take a closer look at how cancer cells are behaving in the body.

“When we explain breast cancer surgery to our patients, we explain that it’s actually two parts,” says Helen Mark, a registered nurse with the Henrietta Banting Breast Centre at Women’s College Hospital.

One part of the surgery involves removing the cancer from the breast – either a lumpectomy or a mastectomy. The second part is lymph node dissection, which is the removal of some or all of the lymph nodes under the arm. The primary goal of lymph node dissection is to provide information about the status of the cancer.

The lymphatic system is a complex network of vessels that carry lymph fluid back towards the heart. Each vessel ends in a node. Every part of the body drains lymph fluid to a specific lymph node. Fluid from the breasts drain to the nodes underneath the arm, which are called axillary lymph nodes (‘axilla’ means underarm).

“If any of the breast cancer cells were going to leave the breast, the first place they would go to is the lymph nodes in the underarm,” Mark explains. “By sampling these lymph nodes we can tell if any of the breast cancer cells have left the breast and possibly spread to other parts of the body.”

Current methods for lymph node dissection focus on the specific nodes that cancer cells will move to first. These are called sentinel nodes. By singling out these nodes, surgeons can remove only one or two lymph nodes instead of removing the entire fat pad containing all of the axillary nodes.

To identify the sentinel nodes, radioactive material or dye is injected into the breast a few hours before surgery, which gives the material time to enter the lymph system, Mark explains.

As the radioactive material and/or the dye moves through the lymph system, the surgeon can use a Geiger counter as well as the visual path of the dye to track the path to the sentinel node or nodes.

“Then they can just remove that primary lymph node, or sometimes there is more than one,” Mark says. Those nodes are then biopsied, looking for cancer cells. “If we can determine that those nodes are negative, we can in most cases safely say that there is a very good chance that all the other ones are negative, too.”

Removing only one, or a few, lymph nodes instead of all of them reduces patients’ post-surgical symptoms such as pain, numbness and the need for a drain under the arm for several days after surgery. It also reduces the risk of developing lymphedema (an accumulation of lymph fluid that causes swelling and pain).

“Most of the time, patients would have axillary (underarm) complications before they had breast complications because the dissection was so much more in depth,” Mark says. “Although some sentinel nodes can be quite deep and may still cause some issues, on the whole, this has significantly reduced the severity of the symptoms after having breast cancer surgery.”