Lymph node sampling

CLICK TO ENLARGE

Because invasive breast cancer tends to spread to lymph nodes and the bloodstream, your doctor will remove some of the lymph nodes under your arm to gauge the extent to which your cancer has spread.

Old approach: Axillary dissection
In the past, doctors used to routinely remove as many of the underarm (axillary) lymph nodes as possible. This approach, called axillary dissection, requires extensive surgery and sometimes leads to complications, including fluid buildup in the arm (lymphedema), infection and numbness.

New approach: Sentinel node biopsy
Doctors now rely on a procedure called sentinel node biopsy to determine if cancer has spread to the lymphatic system. The sentinel lymph node is the first lymph node to which a tumor drains. By finding the sentinel node before surgery, doctors can remove the node for study during surgery. Removing the sentinel lymph node, or nodes, also carries with it the possibility of lymphedema, although neither the extent nor the risk is as great as with axillary dissection.

If the sentinel node is free of cancer, the cancer isn't likely to have spread and further removal of lymph nodes is typically unnecessary. The presence or absence of cancer in the lymph nodes of your armpit is important for determining treatment after the operation.

Locating the sentinel node
One way to find the sentinel node is to inject a harmless dye into the breast, near the tumor. The dye is taken up by the lymphatic channels and delivered to the lymph nodes. Another method is to inject a bit of radioactive solution near the tumor and use an instrument called a gamma detector to see where the radioactivity accumulates. Sometimes both methods are used.

If cancer is detected
If the sentinel node is malignant, further node dissection is needed to determine the stage of lymph node involvement. Further node dissection is also necessary if the sentinel node can't be identified using these techniques. Once identified, the sentinel node is removed during lumpectomy or mastectomy and examined under a microscope. A few medical institutions use a technique called frozen section to evaluate the lymph node tissue and gain preliminary information about its status during the operation. If the surgeon has this information while you're still in the operating room, you may not have to undergo an additional operation.

After the procedure
After the operation, you'll probably have one or two tubes left in place to drain fluid from under your armpit. Since these tubes typically stay in for a few days, you may go home with them in place. Once the drainage has ceased, your surgeon removes the tubes in a simple outpatient procedure.