Multivariable analysis of validation cohort demonstrated that PMS2 mutation was associated with better OS (HR= 0.10; 95%CI, 0.01-0.71; P = 0.021), after adjusting for age, gender, metastasis type, ICI type….Analysis of discovery and validation cohort data shows PMS2 mutation is associated with better OS in ICI-treated patients. These findings indicates that PMS2 mutation may serve as a potential predictive biomarker for ICIs in melanoma.