Sentinel Node Biopsy

Sentinel Lymph Node Biopsy is a way of finding out if a cancer has spread, so that the right treatment can be given to every patient.

When a cancer spreads, cells break off from the tumour and are carried away by the lymph – the watery fluid that surrounds all the cells in our bodies. In many cases these cancer cells become trapped in one of the 500 or so lymph nodes that are distributed around the lymphatic system. Lymph nodes are bean-shaped, ranging from a few millimetres to 1–2 centimetres in size, and they act as filters to clean the lymph as it passes through. The node nearest the tumour – the sentinel node – is the first place that a second cancer will form.

The problem is to locate and test the sentinel node for a given patient, so that the doctors can know whether or not the cancer has spread, and whether further surgery, and additional post-operative chemotherapy and radiotherapy, is needed. Knowing for sure whether the cancer has spread can also be a great source of comfort for the patient.

In breast cancer, a tracer dye is injected near the tumour, and can be detected a little while later as it is trapped by one of the 30 or so lymph nodes in the armpit. When the sentinel node has been located, it is carefully removed by keyhole surgery – this is called a biopsy – and sent for microscopic examination. Often the pathologist finds that the cancer has not spread, in which case it is only the primary tumour that has to be removed.