Background: The pathologic status of the sentinel lymph node (SLN) is a powerful prognostic factor for patients with intermediate thickness melanoma. We hypothesize that a high number of SLNs identified may be associated with poor outcome.
Methods: We evaluated the impact of number of SLNs removed in patients undergoing SLN mapping for cutaneous melanoma at our institution between 1996 and 2006. We excluded patients with multiple primary or synchronous primary lesions (n = 144) to eliminate any chance of erroneous association between a SLN and the wrong primary melanoma. We also excluded patients with in-transit disease (n = 37) and one patient in whom no SLN was identified, leaving 970 patients. We evaluated factors associated with the number of SLNs removed by multivariate Poisson regression and determined whether an increased number of SLNs was associated with poorer overall (OS) or recurrence-free survival (RFS).
Results: Clinical factors independently associated with increased number of SLNs were younger age and head and neck primary site. Pathologic factors associated with an increased number of SLNs were lymphovascular invasion and increased Breslow thickness. There was no association between number of SLNs removed and OS or RFS in all patients or in patients with negative SLNs (n = 803).
Conclusions: The number of SLNs identified during staging of the regional nodal basin for primary melanoma is not an independent prognostic factor. Drainage to multiple SLNs is more common in the setting of an increased Breslow depth and lymphovascular invasion suggesting that tumors with these adverse features may enhance peritumoral lymphangiogenesis.