Analysis of PDAC tumors from human patients revealed that CD8+ T cells, Tregs (FoxP3+), B cells (CD20+), and natural killer (NK) cells (CD56+) could not penetrate the juxtatumoral stromal compartment (within 100 μm of tumor cells) efficiently, as the higher percentage was detected in the pan-stromal compartment (the rest of the tumor). This evidence concerns the gene CD8A and neoplasm.