Minimally invasive staging of patients with melanoma: sentinel lymphadenectomy and detection of the melanoma-specific proteins MART-1 and tyrosinase by reverse transcriptase polymerase chain reaction

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Abstract
A minimally invasive standard has yet to be developed for sentinel lymphadenectomy, and many patients undergo this procedure in the main operating room under general anesthesia. These patients often have microscopic metastases in sentinel nodes that could be missed by histopathologic examination. Techniques of reverse transcriptase polymerase chain reaction (RT-PCR) could detect these metastases if the nodes could be preserved intraoperatively. Fifty patients with melanoma > or = mm thick underwent sentinel lymphadenectomy under local anesthesia in an outpatient surgical unit. Sentinel nodes were identified using blue dye and technetium-99 sulfur colloid and a hand-held gamma probe. Each node was sectioned, with half sent for routine histopathologic study and half preserved in liquid nitrogen. We used RT-PCR to detect mRNA for tyrosinase and Melanoma Antigen Recognized by T cells-1 (MART-1). All patients were able to tolerate sentinel lymph node biopsy under local anesthesia. Sentinel lymph nodes were obtained in 100% of our patients, and usable mRNA was harvested from all but five. Ten patients had positive sentinel node(s) by standard histopathologic examination, and all of these nodes were also positive for MART-1 and tyrosinase. Three patients with negative results by histopathology had positive results by RT-PCR analysis. The average cost of these outpatient operations was 38% less than the same operations performed in the main operating room under general anesthesia. Sentinel lymphadenectomy under local anesthesia in an outpatient setting and intraoperative lymph node preservation in liquid nitrogen are both feasible. Both tyrosinase and MART-1 are promising markers in the detection of occult melanoma in lymph nodes.