PRAME immunohistochemistry demonstrates high diagnostic accuracy for distinguishing melanoma from nevi but no observed association with pT stage in cutaneous melanoma: a Vietnamese clinicopathological study

Background PRAME immunohistochemistry is a useful adjunct in distinguishing melanoma from benign melanocytic lesions, but its clinicopathologic associations remain incompletely understood, particularly in underrepresented populations. Methods This retrospective study included 90 primary melanomas and 90 melanocytic nevi from a Vietnamese cohort. PRAME expression (clone EPR20330) was assessed using a semi-quantitative scoring system: 0 (0%), 1+ (1–25%), 2+ (26–50%), 3+ (51–75%), and 4+ (> 75% of tumor cells with nuclear positivity), with 4 + defined as high expression. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis, and associations with clinicopathologic variables were analyzed using logistic regression. Results The mean age of melanoma patients was 56.4 ± 15.9 years, with a median tumor size of 30 mm. Nodular melanoma was the most common subtype (60%), and mucosal melanoma accounted for 15.6%. Adverse features were common, including Breslow thickness > 1 mm (87.8%), mitotic rate > 1/mm² (85.6%), and ulceration (36%). High PRAME expression was observed in 73.3% of melanomas, whereas 97.8% of nevi were negative and none showed PRAME ≥ 2+. PRAME demonstrated excellent diagnostic performance (AUC 0.936), with sensitivity, specificity, and accuracy of 87.8%, 97.8%, and 92.8% at a cutoff of ≥ 1+. Tumor size > 12 mm was independently associated with high PRAME expression in the overall cohort but not in cutaneous melanoma. No statistically significant associations were observed between PRAME expression and tumor stage in cutaneous melanoma. Conclusions In this predominantly advanced-stage Vietnamese cohort, PRAME immunohistochemistry showed high sensitivity and specificity in distinguishing melanoma from nevi; its performance in early or thin melanomas and its broader clinicopathologic significance remain to be clarified in future studies.