Introduction

The localization, excision, and pathologic evaluation of the sentinel node for the purpose of gaining cancer staging information is called Sentinel Node Biopsy (SNB), or interchangebly, Intraoperative Lymphatic Mapping (ILM). In theory, the histology of the SLN should be highly predictive of the remainder of the lymphatic basin, a theory which has been proven clinically for melanoma and breast cancer. Currently, SNB is considered standard of care when used in cases of melanoma. It is still considered investigational for use in breast cancer, but is gaining broad support and there are indications that the procedure will be standard of care in the near future. This procedure is beneficial in that it will replace full nodal dissection for a majority of patients, thus avoiding the complications associated with full nodal dissection. Typically in a full axillary dissection, 10-25 nodes are removed and analyzed. With SNB, 1-3 sentinel nodes will be excised and analyzed, thereby greatly reducing or eliminating the complications associated with full dissection.

Injection

Melanoma

Breast Cancer

Migration time-SLN should visualize by lymphoscintigraphy in 1-3 hrs.

Imaging

Melanoma

Patient should be placed in operative position, if possible. Immediate dynamic imaging of the injection site, 5 min/frame up to 30 min. Follow with static imaging of the expected draining node basin, in ant/post projections. Lateral or oblique views should be taken if drainage is visualized to the axilla. Once the SLN is visualized, images of the area with the body outline delineated should be obtained. For lesions of the trunk, all possible nodal basins should be imaged, including the pelvis. SLN should be localized and marked under camera with radioactive marker, as well as marked on skin. Films should accompany patient to OR.

Breast Cancer

Patient should be placed in operative position, if possible (arm up). Immediate dynamic imaging is generally unnecessary, due to the longer migration time as compared to melanoma. Static imaging of the injection site including the axilla, supraclavicular, and internal mammary node regions should begin no sooner than 45 min. Ant/post as well as lateral or oblique projections should be obtained. Once the SLN is visualized, images of the area with the body outline delineated should be obtained. SLN should be localized and marked under camera with radioactive marker, as well as marked on skin. Films should accompany patient to OR.

Surgery

Prior to patient prep, the surgeon may wish to externally localize the SLN with the probe, checking his findings against any markings by Nuclear Medicine. This may help to reduce the patient's time under general anesthesia, if it is to be used. The nodal basins are scanned, moving the probe in a grid pattern over the skin. The audible range of the probe should be adjusted (range adjustment x1, x10, x100) according to the signal intensity, always starting on the x1 setting. The SLN in the basin is identified by an intense focus of radioactivity (hot spot). The hot spot should be demonstrated in 2 directions, and the probe manipulated in all directions to precisely localize the point of highest activity. An X should be placed over the localized SLN. Any findings differing from existing markings should be clearly marked. Changes in patient positioning will account for changing location of hot spot.

LYMPHAZURIN* 1% Blue Dye should be injected 5-10 min. before start of surgery. A 5 minute massage of the area injected with LYMPHAZURIN* 1% Blue Dye will greatly facilitate uptake in the nodes.

During the surgery, the SLN location is again confirmed with the probe and a small incision is made over the overlying skin. Guided intraoperatively by the probe, the node is found in situ and excised. The activity level of the node is checked ex vivo by either a count/second reading or a 10-second count. This count is recorded, as the activity of any further radiolabeled nodes will be compared to the activity of the SLN. The nodes that have radioactive counts of at least 10% of the hottest lymph node are considered to be sentinel nodes. The basin from which the SLN was excised should be re-examined with the probe for any residual activity. Any further hot nodes should be counted in situ, and those with activity over 10% of the SLN should be excised. Notice should be made of any blue stained nodes, as they should also be excised, whether hot or cold.