A sentinel node biopsy is usually performed at the same time as surgery to remove a breast tumour.
Before the operation, radioactive material is usually injected into the affected breast – generally on the day of surgery or the previous day if required.
Then during surgery, the surgeon usually injects some blue dye into the breast. Those lymph nodes which are blue, or “radioactive” when probed intraoperatively with a handheld radiation counter, are the ‘sentinel nodes’. The surgeon removes all the blue and radioactive nodes and sends them for pathology to determine whether there is any cancer present in these nodes.