The sentinel node is the first draining lymph node from the site of the melanoma. It is thought that if this node is clear of melanoma cells then the cancer has not yet metastasised.
The sentinel node is located through triple assessment. Firstly a pre-operative injection of technicium99 and a lymphoscitogram, followed by injection of vital blue dye in the anaesthetic room, which helps to visualise the node. During the operation the node is identified using a gamma probe and then visualised with the dye.