ARID1A and neoplasm: Moreover, ARID1A/B2M mutant samples exhibited lower infiltration of key antitumor immune cells, such as myeloid dendritic cells, B cells, and class-switched memory B cells, indicating diminished immune surveillance within the tumor microenvironment.38 The downregulation of critical immune pathways, including those involved in antigen presentation via downregulation of HLA genes38 may further explain the compromised efficacy of dCRT in these patients.