Primary Melanoma Histopathologic Predictors of Sentinel Lymph Node Positivity: A Proposed Scoring System for Risk Assessment and Patient Selection in a Clinical Setting

Background and Objectives: The careful selection of adequate SLNB candidates not only aims at reducing the surgical risk while identifying SLN metastasis, but also plays a crucial role in identifying the patients eligible for adjuvant therapy. Objectives: The purpose of our study was to investigate the clinical and histologic aspects of primary melanomas that correlate with the likelihood of a positive SLNB result. Materials and Methods: A total of 101 primary melanoma patients who underwent sentinel lymph node biopsies were included in the study. General patient demographics were obtained as well as localization and melanoma-specific characteristics of primary melanoma from histologic reports in addition to data derived from SLNB melanoma histopathology reports. Results: The patients with positive SLN results had a statistically significant increased Breslow thickness (3.8 mm vs. 1.97 mm, p = 0.002), higher mitotic index rate (5/mm² vs. 2/mm², p = 0.009), as well as the presence of ulceration (68.4% vs. 31.6%, p = 0.007). Univariate regression analysis showed the Breslow thickness (p = 0.008), the mitotic index rate (p = 0.054), the presence of ulceration (p = 0.009), as well as the pT3-4 stage (p = 0.009) to be significant predictors of SLN positivity. The optimal cut-off values for Breslow thickness and the number of mitoses scores were determined based on ROC curve analysis. Using the Breslow thickness, mitotic index rate, presence of ulceration, and pT3-4 stage significant coefficients from the univariate regression model, a chance prediction score was developed. Conclusions: The newly developed and proposed scoring system can aid in patient selection for SLN biopsy by facilitating a more efficient risk assessment in the detection of lymph node metastases in melanoma patients.