Sentinel Node Biopsy for Malignant Melanoma: Analysis of a Four-Year Experience

Abstract

Aims and background

Sentinel node (SN) biopsy has been introduced to solve the controversy concerning the effectiveness of prophylactic lymphadenectomy in intermediate thickness melanoma. The aim of this study was to evaluate the rate of metastases, the technical details of the procedure, and the main reasons of failure.

Methods

235 patients affected by intermediate thickness melanoma (tumor thickness >0.75 mm and <4 mm) without clinical signs of systemic spread (N₀M₀) were submitted to sentinel node biopsy between 1996 and 2000. Preoperative lymphoscintigraphy was routinely performed in the last 184 patients. Intraoperative mapping with gamma probe was combined with the use of vital dye for identification of sentinel nodes in the last 113 patients.

Results

The SN detection rate was 95.6%, with significant differences depending on the site of dissection and the use of a gamma probe. The overall rate of micrometastases was 14.7%, but relevant differences were recorded between different subgroups of patients (T₂, 5.1%; T_3a, 19.6%; T_3b, 29%).

Conclusions

Sentinel node biopsy requires a multidisciplinary approach (surgery, pathology and nuclear medicine) for reliable results. The association of vital dye and intraoperative gamma probe for sentinel node harvesting has made the procedure more effective, less time-consuming and less invasive. Failures may be due not only to surgical mistakes, but also to improper nuclear medicine procedures or inaccurate histological evaluation of SNs. Methods for histological examination of the SN are still debated and not standardized but promising results have recently been obtained with molecular oncology techniques (RT-PCR).