Lymphatic mapping by sentinel lymph-node (SLN) detection offers a means of assessing the lymph-node status of primary tumours with respect to metastases, without having to resort to formal lymphadenectomy. The SLN procedure usually involves injection of radiocolloid at the tumour site the previous day, and injection of patent blue dye just before surgery. The clinical value of SLN biopsy is based on its reliable negative predictive value and high sensitivity to detect metastatic disease. A full lymphadenectomy...