Size of sentinel node metastases predicts other nodal disease and survival in malignant melanoma

Background A positive sentinel lymph node (SLN) biopsy is an indication for completion lymph node dissection (CLND) in malignant melanoma; however, most CLNDs are negative. We hypothesized SLN metastatic size of ≤2 mm would predict CLND status and prognosis. Methods We evaluated 80 consecutive patients undergoing CLND for positive SLNs over a 10-year period. Incidence of positive nonsentinel nodes and survival were compared for patients with SLN metastases ≤2 mm and >2 mm. Results Of 504 patients undergoing SLN biopsy, 49 patients had SLN deposits ≤2 mm and a 6% incidence of positive CLNDs. Five-year survival was 85%, essentially the same as negative SLN biopsies. In contrast, 31 had SLN metastases >2 mm, a 45% incidence of addition disease at CLND, and 5-year survival of 47% (P < .0001). Conclusion An SLN metastatic cut point of 2 mm is an efficient predictor of CLND status and survival in malignant melanoma.