Sentinel nodes outside lymph node basins in patients with melanoma

Background: Lymphoscintigraphy occasionally reveals hot spots outside lymph node basins in patients with melanoma. The aim of this study was to evaluate such abnormally located hot spots. Methods: Sentinel node biopsy was studied prospectively in 379 patients with clinically localized cutaneous melanoma. One day after lymphoscintigraphy, sentinel node biopsy was performed guided by vital blue dye and a gamma ray detection probe. Results: Persisting hot spots outside the regional node basins were seen in 25 patients (6.6 per cent). Several specific drainage patterns were discerned. In five patients, aberrant sentinel nodes were not explored. The hot spot represented a lymphangioma in two patients. Radioactive lymph nodes were identified in the remaining 18 patients (4.7 per cent). Four patients had metastasis in one of these aberrant lymph nodes. Conclusion: Sentinel nodes were found outside a lymph node basin in 5 per cent of patients. Particular drainage patterns exist. It is recommended to incorporate such sites in the late scintigraphy images and to pursue aberrant sentinel nodes, as they may be the only sites of metastasis.