Lymphatic mapping and sentinel lymph node biopsy in breast cancer

Lymphatic mapping with selective lymphadenectomy is an attractive approach in breast-cancer patients. It uses existing technology to exploit logical anatomic and physiological principles to identify occult regional lymph-node metastases. The lymphatic flow is visualized and the first (sentinel) lymph node on a direct drainage pathway from the primary tumour is identified. This is the node at greatest risk of harbouring metastatic deposits. Retrieving this node requires a concerted effort from the nuclear medicine physician, surgeon and pathologist. Lymphoscintigraphy can indicate the number of sentinel nodes and their location. The surgeon can use two techniques to find the node. A vital dye injected at the tumour site will stain the lymphatic duct as well as the sentinel node and allow their visual identification. Alternatively, a lymph-node-seeking radiopharmaceutical will also migrate from the tumour site to the sentinel node and will enable its retrieval with the use of a gamma detection probe. The pathologist has a number of techniques to identify tumour deposits in the lymph node. A review of the literature shows that the sentinel node can be found in more than 90% of the patients. With experience, the false-negative rate can be kept down to about 5%. This novel approach of lymphatic mapping with selective lymphadenectomy may lead to a substantial reduction in the need for axillary node dissection in patients with breast cancer without compromising survival and regional control, and without loss of prognostic and staging information. This development will translate into a great reduction in patient morbidity and medical expenses.