Hypothesis: For patients with melanoma, interval or intransit sentinel lymph nodes (SLNs) have the same risk for nodal metastasis as SLN in traditional (ie, cervical, axillary, and inguinal) nodal basins. Design: Prospective clinical trial. Setting: Multicenter study. Patients: Eligible patients were aged 18 to 70 years with melanomas of at least 1.0-mm Breslow thickness and nodes with clinically negative findings. Intervention: Sentinel lymph node biopsy was guided by preoperative lymphoscintigraphy to identify all SLNs. Main Outcome Measures: We evaluated interval nodal sites, including epitrochlear, popliteal, and subcutaneous or intramuscular nodes outside of traditional basins, for the presence of metastases. Results: The SLNs were identified in 2332 nodal basins from 2000 patients. In 62 patients (3.1%), interval SLNs were identified. We found SLN metastases in 442 (19.5%) of 2270 conventional nodal basins and 13 (21.0%) of 62 interval sites. In 11 (84.6%) of the 13 cases in which we found an interval node that was positive for metastatic disease, it was the only site of nodal metastasis. Conclusions: Although interval SLNs are identified infrequently, they contain metastatic disease at nearly the same frequency as SLNs in cervical, axillary, and inguinal nodal basins. Positive interval SLNs are likely to be the only site of nodal metastasis. Therefore, detailed preoperative lymphoscintigraphy and meticulous intraoperative search for interval nodes should be performed.
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