Clark level risk stratifies patients with mitogenic thin melanomas for sentinel lymph node biopsy

Area of Science:

• Oncology
• Dermatology
• Surgical Pathology

Background:

• The utility of sentinel lymph node biopsy (SLNB) in thin melanoma (≤1 mm) is debated.
• Identifying predictors of SLN positivity is crucial for patient selection.

Purpose of the Study:

• To investigate predictors of sentinel lymph node positivity in a large cohort of patients with thin primary melanoma.
• To risk-stratify patients with thin melanoma for SLNB based on clinicopathologic factors.

Main Methods:

• Retrospective analysis of 781 patients with thin melanoma who underwent SLNB (1995-2011).
• Univariate, multivariate regression, and classification and regression tree (CART) analyses were used to identify predictors of SLN positivity.
• Clinicopathologic data, including mitotic rate and Clark level, were evaluated.

Main Results:

• Overall SLN positivity rate was 3.7% (29/781 patients).
• Significant predictors of SLN positivity included mitotic rate (OR 7.01) and Clark level IV-V (OR 3.45) in multivariate analysis.
• CART analysis revealed lower SLN positivity in nonmitogenic lesions (0.7%) versus mitogenic lesions (5.6%), with higher rates in mitogenic lesions with Clark level IV-V (8.2%).

Conclusions:

• SLN positivity is low in thin melanoma, especially in nonmitogenic lesions.
• Mitotic rate and Clark level IV-V are significant predictors of SLN positivity in thin melanoma.
• These factors can aid in selecting appropriate thin melanoma patients for SLNB.