Determining whether the breast cancer has spread to the lymph nodes under the arm is a critical part of staging the cancer. Statistically, about 30% of those diagnosed with breast cancer have disease in their lymph nodes and 70% do not. Traditionally, an “axillary dissection”, which removes all of the nodes under the arm along the chest wall, was performed in order to distinguish between these two groups. This procedure puts women at risk for developing painful swelling and arm immobility, and confers no benefit to those whose nodes are negative. For these reasons, a new technique known as the sentinel lymph node biopsy was developed. This procedure allows the surgeon to identify and test the first lymph node in the chain of nodes under the arm rather than just removing them all.
The technique is simple. A tracer solution with a faint radioactive signal is injected into the breast around the nipple just before the operation. This tracer solution is picked up by the lymphatic channels and carried to the axillary lymph node chain. Then, in the operating room, a blue dye is injected similarly, and the dye travels quickly in those same lymphatics to the sentinel node. A small incision is then made under the arm, and the blue node that has a faint radioactive signal is identified and removed. The pathologist looks at this node under the microscope and if no cancer is present there, then no further lymph node removal is required. If cancer is found in the sentinel node, then an axillary dissection in order to ensure that no cancer is left behind.
Women who undergo a sentinel node biopsy generally recover uneventfully from that procedure with no long term consequences for their arm function. Women who have a positive sentinel node and then undergo an axillary dissection are at risk for chronic swelling of the involved arm, known as “lymphedema,” as well as chronic pain and changes in sensation and mobility that can be bothersome. These women benefit from physical therapy with a lymphedema specialist who can help them prevent or control the swelling and regain their arm mobility after the operation