The prognostic importance of sentinel lymph node biopsy in thin melanoma

Background: Sentinel lymph node biopsy (SLNB) is prognostically useful in patients with cutaneous melanoma with Breslow thickness > 1 mm. The objective of this study was to determine whether sentinel node histology has similar prognostic importance in patients with thin melanomas (<= 1 mm). Methods: This was a retrospective study of patients who underwent SLNB for clinically localized melanoma at Indiana University Medical Center between 1994 and 2003. SLNB results and traditional melanoma prognostic indicators were studied in univariate log-rank tests. Results: One hundred eighty-four patients with melanomas <= 1 mm thick underwent SLNB. SLNB was tumor positive in 12 patients (6.5%). Univariate analysis of SLNB results revealed that Breslow thickness, Clark level of invasion, and mitotic index were associated with SLNB status. Tumor positivity was observed at different rates in tumor thickness subsets: <.75 mm, 2.3%; and .75 to 1.0 mm, 10.2% (P = .0372). Disease-free survival and overall survival were significantly associated with SLNB results in melanomas <= 1 mm (log-rank test: P < .0001 and P = .0125, respectively) at a median follow-up of 26.3 months. Conclusions: SLNB histology in melanomas <= 1.0 mm deep is a significant predictor of outcome. SLNB should be considered for selected patients with melanomas .75 to 1.0 mm.