The procedure provides a “road map” showing the direction of lymphatic drainage from around the site of a cancer.
The Sentinel Node study demonstrates the path of lymphatic drainage. This allows the surgeon to take out the specific node (or nodes) that are the first to receive lymphatic drainage from the area around the tumor. If these “sentinel” node(s) do not show any microscopic evidence of tumor, it is very unlikely that any other nodes would contain any tumor cells.
The procedure involves no preparation on the part of the patient, other than the usual pre-operative instructions provided by the surgeon.
In nuclear medicine, staff will inject a small amount of radioactive tracer in the region of the tumor.
The rest of the exam consists of taking pictures. The technologist will take images of the lymph nodes draining the region around the tumor. If lymph nodes are seen, the nuclear medicine staff may use a pen to put a mark on the skin overlying the lymph node to help the surgeon find the nodes.
In the operating room, the surgeon has a probe that detects the radioactivity in the lymph nodes. The probe is used in conjunction with the pictures and skin marks from nuclear medicine to identify the sentinel node(s). Once the nodes are removed, they are sent to pathology for microscopic examination for evidence of spread of the tumor.