Sentinel lymph node biopsy and melanoma biology.

Minimally invasive intraoperative lymphatic mapping and sentinel node biopsy has become the standard approach for staging the regional lymph nodes for early-stage melanoma. The procedure requires close collaboration of surgeon, pathologist, and nuclear medicine physician. The strength of lymphatic mapping and sentinel node biopsy is its accuracy of detecting occult lymph node metastases. Reverse transcriptase-PCR (RT-PCR) analyses of either fresh-frozen or paraffin-embedded sections of the sentinel lymph nodes have been found to be more sensitive than H&E staining or immunohistochemistry techniques, but lack of specificity and limits in the availability of tissue specimens make this technique impractical for routine use. Three randomized clinical trials are examining the therapeutic value of lymphatic mapping and sentinel node biopsy for melanoma. Preliminary results of the Multicenter Lymphadenectomy Trial I show the high level of accuracy and low morbidity of lymphatic mapping and sentinel node biopsy done through an international working group. The therapeutic value of lymphatic mapping and sentinel node biopsy is still unclear. Multicenter Lymphadenectomy Trial II will test the clinical significance of lymph nodes evaluated by RT-PCR and the value of completion lymph node dissection for patients found to have tumor-positive sentinel lymph nodes by H&E, immunohistochemistry, or RT-PCR. The Sunbelt Melanoma Trial examines the therapeutic value of completion dissection and benefits of Intron A. The ability to detect occult nodal metastases and evaluate the interaction of primary tumor with the regional lymph nodes may provide for better understanding of the metastatic process in patients with melanoma and help to determine the function of the regional lymph nodes as markers of metastases or incubators of tumor cells in the metastatic cascade.