Tumor-infiltrating lymphocytes in primary tumors of colorectal cancer and their metastases

The presence of tumor cells in the large intestine stimulates hypoxia and local inflammatory mediators that activate numerous inflammatory cells, including a diverse lymphoid tumor cell population. The aim of the present study was to evaluate tumor-infiltrating lymphocytes (TILs) located in the invasive primary tumor, surrounding deposits of tumor cells and those present in distal metastatic cells in the liver of patients with colorectal cancer. Furthermore, the correlation of TILs with anatomical parameters was assessed. The study group included 123 patients with primary tumor colorectal cancer without distant metastasis, 25 cases with deposits of colorectal cancer cells and 15 cases of colorectal cancer liver metastasis. TILs were assessed in tissues stained with hematoxylin-eosin using light microscopy and evaluated by two independent pathologists blinded to the clinical information. Infiltration of TILs in the invasive front of primary tumor was stronger compared with those surrounding deposits of cancer cells and liver metastases (P<0.001). TILs in the invasive front of primary tumor masses were associated with various variables linked with tumor progression and inflammatory cell infiltrate. TILs distributed around the deposits of cancer cells were associated with postoperative treatment; however, those localized in the invasive front of liver metastases were correlated with preoperative therapy. In conclusion, TILs assessment in primary tumors of colorectal cancer, surrounding deposits of tumor cells and in the metastatic cells in the liver may be helpful in understanding the role of these cells in the organization of immune response.