MRC1 and neoplasm: We investigated MMR, ARID1A, p53, PD-1, PD-L1 (combined positive score ≥1 deemed PD-L1 positive; combined positive score <1 deemed PD-L1 negative) and combined PD-1/PD-L1 protein expression in archival tumor samples to explore their relationship with clinical outcome following ICI treatment.