How is the sentinel node located during a biopsy?

The sentinel node is located during a biopsy primarily by injecting a small amount of a radioactive substance or blue dye. This technique is crucial in identifying the first lymph node that receives drainage from a tumor site, known as the sentinel lymph node. The injection allows the surgeon to trace the flow of the dye or the radioactive substance through the lymphatic system, thereby pinpointing the sentinel node with high accuracy.

This method is advantageous because it provides real-time information about the lymphatic pathways and helps in ensuring that only the relevant lymph nodes are biopsied. If the sentinel node is positive for cancer, it can guide the decision for further treatment, while minimizing unnecessary removal of additional lymph nodes that may not be affected.

Other methods, such as imaging the lymphatic system or using ultrasound, may provide some information but are generally less practical or direct compared to the more established technique of injection. A surgical incision is involved in the actual biopsy but does not play a role in locating the sentinel node initially; rather, it is a step that follows the identification of the node.