Reproducibility of lymphoscintigraphy in cutaneous melanoma: Can we accurately detect the sentinel lymph node by expanding the tracer injection distance from the tumor site?

The aim of the study was to determine whether the sentinel lymph node (SLN) can be accurately detected in cutaneous melanoma patients when the injecti on distance from the tumor site is expanded. Methods: In 100 patients with cutaneous melanoma, lymphoscintigraphy was performed twice. First, we injec ted 37 MBq Tc-99m nanocolloid intracutaneously at a 2- to 5-mm distance fro m either the melanoma or the biopsy scar. The injection was followed by dyn amic imaging, which continued until the SLN became visible. On another day, we repeated the investigation, injecting the radiopharmaceutical intracuta neously exactly 10 mm from the previous injection site. The detected SLNs o f both investigations were compared to determine the number and location of SLNs for each patient. Results: The SLN identification rate was 94% with c lose injection and 100% with 10-mm-distant injection. All SLNs detected wit h close injection were visible with distant injection. In 84 of 100 patient s, the images of both investigations showed the same number and location of SLNs. In the remaining 16 patients, an additional SLN was detected with th e distant injection. Conclusion: The reproducibility of lymphoscintigraphy using different injection distances was 84%. The discordance in the remaini ng 16% was caused by detection of a lymph node in addition to the original SLN with distant injection. Diagnostic excision of the primary tumor before lymphoscintigraphy was possible without preventing detection of the origin al SLN. However, in 16% of our patients, excision of an additional lymph no de had to be considered when lymphoscintigraphy was performed after diagnos tic excision.