The sentinel node is the first node into which the lymph system drains. By removing and examining the sentinel node, a surgeon can determine if breast cancer has spread to the lymph nodes. But how does the surgeon locate the sentinel node?

The surgeon pinpoints the sentinel node by injecting a contrast medium (a blue dye and/or a radioactive tracer) into the tumor area. The lymphatic vessels then carry the contrast media into the first node in that system, the sentinel node. There the blue dye collects and is visible to the surgeon, or the radioactive tracer may be detected by a Geiger counter.

Sentinel Node Biopsy