Detection of melanoma micrometastasis in sentinel nodes by reverse transcription-polymerase chain reaction correlates with tumor thickness and is predictive of micrometastatic disease in the lymph node basin

The sentinel node has been reported to be representative for the presence o r absence of metastatic melanoma in the draining lymph node basin. In this study, for the first time sentinel nodes and adjoining nonsentinel nodes we re analyzed for micrometastatic disease using tyrosinase reverse transcript ion-polymerase chain reaction (RT-PCR) in comparison with standard immunohi stochemistry. Successful identification of the sentinel nodes using a gamma probe-guided surgery was achieved in 73 (92%) of 79 patients with cutaneou s stage I and II melanoma (tumor thickness greater than or equal to 0.75 mm ). A total of 794 regional lymph nodes, 148 sentinel nodes, and 646 adjoini ng nonsentinel nodes were evaluated. Tyrosinase RT-PCR was shown to increas e the sensitivity for melanoma cell detection in sentinel nodes significant ly (49% positivity) as compared with immunohistochemistry using antibodies against HMB-45 antigen and S-100 protein (18% positivity). Examination of s entinel nodes was highly predictive in determining the presence of regional lymph node micrometastasis by immunohistochemistry (99%) and RT-PCR (89%). Interestingly, detection of nodal micrometastasis by RT-PCR showed a stron g positive correlation with tumor thickness of primary cutaneous melanoma. These results suggest the clinical significance and emphasize the importanc e of tyrosinase RT-PCR for detection of melanoma micrometastasis in sentine l nodes.