The impact of dynamic lymphoscintigraphy and gamma probe guidance on sentinel node biopsy in melanoma

In cutaneous melanoma, biopsy of the first tumour-draining lymph node (sentinel node, SN) may replace routine elective lymph node dissection (ELND). Even in experienced hands the original technique using vital dyes fails to localise the SN in 20% of cases. In this study we investigated whether the procedure benefits from lymphoscintigraphy and the use of a gamma probe. In 41 patients technetium-99m-colloidal albumin was injected intracutaneously around the scar of the excised tumour. This was followed by dynamic and late static imaging. The first focal accumulation was assumed to be the SN. In all patients at least one SN was found, in 95% within the first 20 min. By showing multiple or ramifying lymphatic channels, dynamic lymphoscintigraphy differentiated between spill and multiple SNs. In all cases the initial focus retained the highest fraction of radioactivity for at least 18 h. The gamma probe was especially useful in the axilla and neck, where it accurately showed the optimal incision site and facilitated the search for deep-seated nodes. Gamma probe-localised SNs were dye-positive in 93% of cases. The SN contained metastases in 20% of the patients. Only in these patients was ELND performed, which revealed that the SN had been the only metastatic node in four of eight cases. We conclude that dynamic lymphoscintigraphy is essential for SN localisation, that tracer kinetics allow flexible timing of surgery, and that the surgical procedure benefits from use of the gamma probe.