Sentinel node localization in cutaneous melanoma: lymphoscintigraphy with colloids and antibody fragments versus blue dye mapping

In stage I cutaneous melanoma, biopsy of the first tumour-draining lymph no de (sentinel node, SN) may replace routine elective lymph node dissection ( ELND). The patent blue dye (PBD) technique has been shown to be an original method for the localization of the SN, but its sensitivity is sometimes un satisfactory, depending on the basin where the SN is located. We compared t hree methods to locate the SN: intraoperative PBD mapping, lymphoscintigrap hy (LS) with an aspecific tracer (colloid) and LS with a specific tracer (m onoclonal antibody, MoAb). Fifty patients with cutaneous melanoma were enro lled in this study. The day before surgery LS was performed following an in tradermal injection of 55 MBq technetium-99m-labelled HSA colloidal particl es (25 patients: group A) or 220 MBq of Tc-99m-F(ab')(2) MoAb 225.28 S (25 patients: group B) around the site of the primary lesion. In group B an equ al amount of tracer was injected, as a control, in the contralateral site. Early and delayed images were acquired with a gamma camera and SN(s) marked on the skin. In all 50 patients the PBD technique was also performed immed iately before surgery. When a blue node was identified intraoperatively, it s radioactivity level was measured with a gamma probe. In the absence of bl ue coloration, the probe alone was used to detect the SN. Lymphoscintigraph ic visualization of SNs was possible in 50/50 patients (100%), a total of 7 3 SNs (38 in group A and 35 in group B) were found, distributed in 55 basin s. Gamma probe detection (GPD) allowed the identification of SNs in 49/50 p atients (98%), and 72 SNs in 54 basins were localized. By contrast, using P BD, SNs were stained only in 40/50 patients (50 SNs in 40 basins). A tumour -positive SN was histologically proven in 13 patients (26%). In group B, no increase uptake was observed in the seven positive SNs (6/25 patients) com pared with the contralateral uninvolved nodes. In conclusion this study dem onstrates that LS combined with GPD is a safe method for detecting SNs and is more sensitive than the PBD technique. The use of MoAb fragments did not show any advantage over the non-specific tracer.