Frequency of nonsentinel lymph node metastasis in melanoma

Background: Completion lymph node dissection (CLND) may not be necessary for some patients because nodal metastasis is rarely detected beyond the sentinel lymph nodes (SLNs). This analysis was performed to determine, among patients with positive SLNs, the rate of nodal metastasis found in nonsentinel nodes (NSNs). Methods: This analysis includes patients with positive sentinel nodes, detected by hematoxylin and eosin (H&E) staining or immunohistochemistry (IHC), who then underwent CLND. Results: This analysis included 274 patients with at least one positive SLN who underwent CLND of 282 involved regional nodal basins. Of the 282 SLN-positive nodal basins, 45 (16%) were found to have positive NSNs in the CLND specimen. Breslow thickness, Clark level, presence of ulceration, histological subtype, presence of vertical growth phase, evidence of regression, presence of lymphovascular invasion, number of positive SLNs, age, sex, and presence of multiple draining nodal basins were not predictive of positive nodes in the CLND specimen. Patients with SLN metastases detected only by IHC had an equal likelihood of having positive NSNs as those patients with positive SLNs on H&E examination. Conclusions: No patient population could be identified with minimal risk of non-SLN metastasis. When a positive SLN is identified on either H&E staining or IHC, CLND should be performed routinely.