AIM:The association of hepatitis C virus(HCV) infection with typeⅡmixed cryoglobulinemia is well established,but the role of HCV in B-cell lymphoma remains controversial.In patients with HCV infection,B-cell clonal expansions have been detected in peripheral blood and bone marrow,and a high prevalence of B-cell non-Hodgkin’s lymphomas has been documented.Liver biopsies in chronic HCV infection frequently show portal lymphoid infiltrates with features of B follicles,whose clonality has not yet been investigated.The object of this study was to determine the frequency of liver-infiltrating monoclonal B-cells in 40 patients with HCV infection.METHODS:Eight hundred and forty-eight patients were studied prospectively,including 40 HCV-positive patients and 808 patients with chronic hepatitis B virus(HBV)infection.Immunohistochemical study for B-and T-cell markers was performed on the paraffin-embedded liver tissue sections.The clonality of lymphoid B-cells was tested using a polymerase chain reaction(PCR)approach designed to identify immunoglobulin heavy chain gene(IgH) rearrangements.RESULTS:Liver-infiltrating monoclonal B-cells were detected in the liver for 4(10%)of 40 HCV-positive patients but were present in only 3(0.37%)of 808 liver biopsy specimens with chronic HBV infection.Chi-square testing showed that the monoclonal B-cells infiltration in the liver was more frequent in the HCV-infected patients(P=0.000).A clonal IgH rearrangement was detected in 5(71.4%)of 7 liver biopsy specimens with monoclonal B-cells infiltration.In 2 of 5 patients with both a clonal B-cell expansion and monoclonal B-cells infiltration in the liver,a definite B-cell malignancy was finally diagnosed.CONCLUSION:Liver-infiltrating monoclonal B-cells are detected in the liver of patients with chronic HCV and HBV infection.A high percentage of patients with monoclonal B-cells infiltration and B-cell clonality in the liver were finally diagnosed as having a definite B-cell malignancy. AIM: The association of hepatitis C virus (HCV) infection with type II mixed cryoglobulinemia is well established, but the role of HCV in B-cell lymphoma remains controversial. In patients with HCV infection, B-cell clonal expansions have been detected in peripheral blood and bone marrow, and a high prevalence of B-cell non-Hodgkin’s lymphomas has been documented. Liver biopsies in chronic HCV infection frequently show portal lymphoid infiltrates with features of B follicles, whose clonality has not yet been investigated. The object of this study was Eight hundred and forty-eight patients were studied prospectively, including 40 HCV-positive patients and 808 patients with chronic hepatitis B virus (HBV) infection . Immunohistochemical study for B-and T-cell markers was performed on the paraffin-embedded liver tissue sections. The clonality of lymphoid B-cells was tested using a polymerase chai HCV reactions (PCR) were designed to identify immunoglobulin heavy chain gene (IgH) rearrangements .RESULTS: Liver-infiltrating monoclonal B-cells were detected in the liver for 4 (10%) of 40 HCV-positive patients but were present in only 3 (0.37%) of 808 liver biopsy specimens with chronic HBV infection. Chi-square testing showed that the monoclonal B-cells infiltration in the liver was more frequent in the HCV-infected patients (P = 0.000) .A clonal IgH rearrangement was detected in 5 (71.4%) of 7 liver biopsy specimens with monoclonal B-cells infiltration. 2 of 5 patients with both a clonal B-cell expansion and monoclonal B-cells infiltration in the liver, a definite B-cell malignancy was finally diagnosed .CONCLUSION: Liver-infiltrating monoclonal B-cells are detected in the liver of patients with chronic HCV and HBV infection. A high percentage of patients with monoclonal B-cells infiltration and B-cell clonality in the liver were finally diagnosed as having a definite B-cell malignancy.