The dense tissue morphology forms a physical barrier that limits the free migration of T cells.8 Some studies have shown that a high blood vessel density is associated with high T-cell and B-cell abundances in tissue sections from patients with solid tumours.9 Some successes have been achieved in animal models by utilising fibroblast activation protein (FAP) CAR-T cells to reduce the number of tumour fibroblasts to counteract these physical barriers.10 Heparanase, an enzyme that degrades the matrix, can promote CAR-T cell infiltration and anti-tumour efficacy in solid tumours.11 This evidence concerns the gene FAP and neoplasm.