Incidence of sentinel lymph node involvement in a modern, large series of desmoplastic melanoma

Background: Recent studies have suggested that sentinel lymph node (SLN) biopsy is of limited value in desmoplastic melanoma. This study was performed to compare the rate of positive SLN biopsy in the Surveillance, Epidemiology, and End Results (SEER) database with that of a multi-institutional clinical trial and to investigate relevant prognostic factors in desmoplastic melanoma. Study Design: Patients with desmoplastic melanoma ≥1.0 mm Breslow thickness, who underwent SLN biopsy in a multi-institutional prospective clinical trial, were combined with a single institution melanoma database (combined database) and compared with patients from the SEER database (1998 to 2009). Disease-free survival (DFS) and overall survival (OS) were summarized using Kaplan-Meier curves and compared using Cox proportional hazard models. Results: The rate of positive SLN in the combined database was 17.0% (8 of 47). By comparison, the rate of positive SLN in SEER was lower: 2.5% (15 of 594). On multivariable analysis, Breslow thickness ≥2.6 mm (hazard ratio 8.17, 95% CI 1.26 to 160.1; p = 0.0259) and an interaction between SLN status and ulceration (p = 0.0013) were independent risk factors for worse OS in the combined database; patients with ulceration and a positive SLN had significantly worse OS. In the combined database on multivariable analysis, SLN positivity (p = 0.0161) and ulceration (p = 0.0004) were independent risk factors for worse DFS. Conclusions: The rate of positive SLN in desmoplastic melanoma may be higher than that reported in the SEER database. Sentinel lymph node biopsy may be considered as part of the comprehensive staging of desmoplastic melanoma ≥1.0 mm Breslow thickness.