Sentinel lymph node biopsy for melanoma: How many radioactive nodes shouldbe removed?

Background: Sentinel lymph node (SLN) biopsy has become a standard methtod of staging patients with cutaneous melanoma Sentinel lymph node biopsy usua lly is performed by intradermal injection of a vital blue dye (isosulfan bl ue) plus radioactive colloid (technetium sulfur colloid) around the site of the tumor. Intraoperative gamma probe detection has been shown to improve the rate of SLN identification compared to the use of blue dye alone. Howev er, multiple sentinel nodes often are detected using the gamma probe. It is not clear whether these additional lymph nodes represent true sentinel nod es, or second-echelon lymph nodes that have received radiocolloid particles that have passed through the hue sentinel node. This analysis was performe d to determine the frequency with which these less radioactive lymph nodes contain metastatic disease when the most radioactive, or "hottest," node do es not. Materials and Methods: In the Sunbelt Melanoma Trial, 1184 patients with cu taneous melanoma of Breslow thickness 1.0 mm or more had sentinel lymph nod es identified. Sentinel lymph node biopsy was performed by injection of tec hnetium sulfur colloid plus isosulfan blue dye in 99% of cases. Intraoperat ive determination of the degree of radioactivity of sentinel nodes lex vivo ) was measured, as well as the degree of blue dye staining. Results: Sentinel nodes were identified in 1373 nodal basins in 1184 patien ts. A total of 288 of 1184 patients (24.3%) were found to have sentinel nod e metastases detected by histology or immunohistochemistry. Nodal metastase s were detected in 306 nodal basins in these 288 patients. There were 175 n odal basins from 170 patients in which at least one positive sentinel node was found and more than one sentinel node was harvested. Blue dye staining was found in 86.3% of the histologically positive sentinel nodes and 66.4% of the(: negative sentinel nodes. In 40 of 306 positive nodal basins (13.1% ), the most radioactive sentinel node was negative for tumor when another, less radioactive, sentinel node was positive for tumor. In 20 of 40 cases ( 50%), the less radioactive positive sentinel node contained 50% or less of the radioactive count of the hottest lymph node. The cervical lymph node ba sin was associated with an increased likelihood of finding a positive senti nel node other than the hottest node. Conclusions: If only the most radioactive sentinel node in each basin had b een removed, 13.1% of the nodal basins with positive sentinel nodes would h ave been missed. It is recommended that all blue lymph nodes and all nodes that measure 10% or higher of the ex vivo radioactive count of the hottest sentinel node should be harvested for optimal detection of nodal metastases .