HLA-C and neoplasm: Compared with MSI-H/dMMR CRC, MSI-L/MSS/pMMR tumors exhibit characteristics such as low tumor mutational burden (TMB), low expression of major histocompatibility complex (MHC) molecules by antigen-presenting cells, inhibited initial activation of T cells, abnormal vascular signaling, and a suppressive tumor immune microenvironment (26).