Extracapsular Spread in Melanoma Lymphadenopathy: Prognostic Implications, Classification, and Management.

Abstract

Extracapsular spread (ECS) is recognized to be a high-risk factor in melanoma patients with macrometastatic (N+) nodal disease; however, ECS risk in sentinel lymph node (SLN) biopsy, micrometastatic stage III disease is ambiguous. The aim of this study was to examine ECS incidence and its prognostic significance. A two-center, retrospective analysis of all patients with micro/macrometastatic lymphadenopathy undergoing nodal surgery from 2008 to 2014 was performed. Patient demographics, tumor characteristics, nodal ECS status, and patient outcomes were collected. Overall, 515 patients with nodal disease were identified (males/females = 277/238); median age was 63years (range 17-94). There was an increased frequency of ECS disease in N+ disease compared with SLN+ disease (52.4% vs. 16.2%; p < 0.0001). The absolute disease-specific survival (DSS) difference for SLN+ patients was approximately 30% at 10years (66.2% vs. 37.2%; p < 0.0001), and the prognosis of SLN+/ECS+ patients was identical to N+/ECS- patients. Multivariate analysis demonstrated that ECS status was an independent prognostic indicator for DSS (hazard ratio 2.47, 95% confidence interval 1.87-3.26; p < 0.0001) in patients with SLN+ disease. There were significant differences in nodal burden according to ECS status between the SLN+ and N+ subgroups suggestive of differing biology in ECS+ tumors. We found that ECS is a significant DSS, progression-free survival, and overall survival indicator in SLN+ and N+ disease. We demonstrated that ECS upstages stage III disease, similar to ulceration in primary melanoma (stage I/II disease). A simplified staging system substituting ECS for N stage accurately stages patients according to prognosis.