The natural history of thin melanoma and the utility of sentinel lymph node biopsy

Background and ObjectivesCurrent literature may overestimate the risk of nodal metastasis from thin melanoma due to reporting of data only from lesions treated with SLNB. Our objective was to define the natural history of thin melanoma, assessing the likelihood of nodal disease, in order to guide selection for SLNB. MethodsRetrospective review. The primary outcome was the rate of nodal disease. Clinicopathologic factors were evaluated to find associations with nodal disease. ResultsFive hundred and twelve lesions, follow up available for 488 (median: 48 months). Lesions treated with WLE/SLNB compared to WLE alone were more likely to have high-risk features. The rate of nodal disease was higher in the WLE/SLNB group (24 positive SLNB, five false-negative SLNB with nodal recurrence: 10.2%) compared to WLE alone (four nodal recurrences: 2.0%). Univariate analysis showed age 45, Breslow depth 0.85mm, mitotic rate >1mm(2), and ulceration were associated with nodal disease. Multivariate analysis confirmed the association of age 45 and ulceration. ConclusionsSLNB for melanoma 0.75-0.99mm should be considered in patients age 45, Breslow depth 0.85mm, mitotic rate >1mm(2), and/or with ulceration. Thin melanoma <0.85mm without high-risk features may be treated with WLE alone.