Previously, women diagnosed with invasive breast cancer would have all the lymph nodes removed from the axilla (armpit) on the affected side. This is called an axillary clearance. A major complication of this surgery was lymphoedema of the arm on the affected side. Lymphoedema is swelling of the arm and hand due to the surgical disruption of the lymph vessels which drain fluid from the arm back into the body. The swollen arm is more prone to infections and skin ulcers. Lymphoedema is usually a chronic and miserable condition, which requires lifelong treatment.

Over recent years a new technique of sentinel node biopsy has been introduced. It is thought that there is a single sentinel (gate-keeper) lymph node in the axilla to which the breast drains and from which all the other lymph nodes are fed. By identifying the sentinel lymph node and removing and testing this node for cancer it is possible to predict if the other nodes will be affected.

If the sentinel node is negative for cancer the other lymph nodes do not need removing. This has resulted in a marked reduction in the number of axillary clearances performed and consequently a dramatic reduction in the number of women with lymphoedema following breast cancer surgery. This has significantly improved the quality of life for these women.

The sentinel node is identified by injecting a small amount of radioactive isotope into the affected breast prior to surgery and a second injection of blue dye into the affected breast at the start of surgery. The radioactivity and blue dye drain to the sentinel node. Using a gamma counter and looking for blue nodes the sentinel node is identified. Most centres are now offering this technique to women if clinically there is no evidence of cancer in the lymph nodes prior to surgery.