AIM: To investigate the role of tumor inf iltrating lym-phocytes (TIL) in primary hepatocellular and cholangio-lar carcinomas of the liver.METHODS: Immunohistochemical analysis was per-formed including antibodies to CD3, CD4, CD8, CD20, CD56 and TIA-1 in formalin-f ixed and paraff in-embed-ded tissue of 35 liver resection specimens of hepatocel-lular or cholangiocellular carcinomas. Semiquantitative evaluation was performed with emphasis on the area of the tumor itself and of the tumor/liver interface.RESULTS: All hepatocellular carcinomas showed in-filtration of lymphocytes predominantly around the tumor in the tumor/liver interface consisting mainly of CD3+ CD4+ T lymphocytes [164.3/10 high power f ields (HPF)] and in the tumor itself of CD8+ cells (54.9/10 HPF). Cholangiocarcinomas contained a heterogeneous amount of TIL, composed mainly of CD3+ T cells with a predominance of CD8+ cells in the tumor tissue (52.6/10 HPF) and of CD4+ cells in the interface region (223.1/10 HPF). CD56+ cells of the innate immune system were scarce. There was no significant difference between hepatocellular or cholangiolar carcinoma. No correlation with the clinicopathological data was seen. CONCLUSION: Liver TIL consists of intratumoral CD8+ T cells and peritumoral CD4+ T cells indepen-dent of histogenetic origin. Different functions of lym-phocytes in these regions seem possible. AIM: To investigate the role of tumor infiltrate lym-phocytes (TIL) in primary hepatocellular and cholangio-lar carcinomas of the liver. METHODS: Immunohistochemical analysis was per-formed including antibodies to CD3, CD4, CD8, CD20, CD56 and TIA -1 in formalin-f ixed and paraff in-embed-ded tissue of 35 liver resection specimens of hepatocel-lular or cholangiocellular carcinomas. Semiquantitative evaluation was performed with emphasis on the area of ​​the tumor itself and of the tumor / liver interface .RESULTS : All hepatocellular carcinomas showed in-filtration of lymphocytes predominantly around the tumor in the tumor / liver interface consisting primarily of CD3 + CD4 + T lymphocytes [164.3 / 10 high power fields (HPF)] and in the tumor itself of CD8 + cells (54.9 / 10 HPF). Cholangiocarcinomas contained a heterogeneous amount of TIL composed mainly of CD3 + T cells with a predominance of CD8 + cells in the tumor tissue (52.6 / 10 HPF) and of CD4 + cells in the interface region (223.1 / 10 HPF) cells of the innate immune system were scarce. There was no significant difference between hepatocellular or cholangiolar carcinoma. No correlation with the clinicopathological data was seen. CONCLUSION: Liver TIL consists of intratumoral CD8 + T cells and peritumoral CD4 + T cells indepen-dent of histogenetic origin Different functions of lym-phocytes in these regions seem possible.