A technique for identifying the initial site of cancer metastasis. After injection of a radioactive tracer directly into the tumor mass, the tissue is massaged to encourage uptake of tracer by lymphatic vessels. A negative biopsy of the first node infiltrated by the tracer suggests that the malignancy has not yet spread to neighboring regional lymph nodes.
A modern procedure is performed to determine the potential spread of breast cancer to the auxiliary (underarm) lymph nodes. In this technique, a blue radioactive tracer and/or blue dye are injected into the region surrounding the breast tumor. The lymphatic vessels then carry this dye or radioactive material to the so-called “sentinel node.” This sentinel node is believed to be the first lymph node that receives fluid from the tumor and is most likely to contain cancer cells if the cancer has metastasized. Additional lymph nodes are only removed if the sentinel node is found to contain cancer cells.