CD8A and neoplasm: Conversely, in group B, the mutational directions were characterized by “forward” mutations in key driver genes in all cases (KRAS and PIK3CA in PAT4, PI3KCA and SMAD4 in PAT5, and PIK3CA and BRAF in PAT6) and tumor immune microenvironment was infiltrated by a significantly low density of GrzB+ CD8+ cells.