PRAME Immunostaining in Acral Melanocytic Proliferations: A Meta-Analysis

Acral cutaneous melanoma is a highly aggressive form of skin cancer that develops in palms, soles, and/or the nail unit. PReferentially expressed Antigen in MElanoma (PRAME) is an immunohistochemical marker that has shown a high degree of expression in cutaneous melanomas. However, no meta-analysis has previously focused on acral melanocytic proliferations. Herein, we performed the first meta-analysis to objectify the utility of PRAME immunohistochemistry, focusing on this understudied subtype of melanocytic proliferations involving acral sites. Thirteen studies were identified, which included 930 lesions (557 malignant and 373 benign). A random-effects model was used to calculate sensitivity, specificity, and likelihood ratios. Summary receiver operating characteristic curves and forest plots were created, and heterogeneity was assessed using Cochran Q and I2 statistics. PRAME expression in acral melanoma showed the highest diagnostic accuracy at a cutoff value of 3+/50%, pertaining to the optimal balance between sensitivity and specificity (78% and 92%, respectively). Although PRAME immunostaining enhances the accurate diagnosis of acral melanocytic proliferations, its expression in atypical and borderline melanocytic proliferations remains controversial and shows considerable variability. Thus, the definitive diagnosis of acral melanoma still relies on careful clinicopathologic assessment and, occasionally, molecular correlation.