Hepatitis B virus in situ hybridization in virus seronegative diffuse large B-cell lymphomas – A pilot study

BACKGROUND: Hepatitis B virus (HBV) is well established to be lymphotropic with replicative intermediates of the virus found in the mononuclear cells and B cells. HBV is also known to persist indefinitely in the form of occult infection (HBsAg negative but HBV DNA positive). Serological and molecular studies and meta-analyses have found a significant association of HBV with diffuse large B-cell lymphoma (DLBCL). Whether the HBV is in the malignant cells or not remains unclear. AIM: To localize viral HBS gene sequences within the malignant cells of DLBCL. SETTINGS AND DESIGN: The study was conducted in the Department of Microbiology on archived lymph node tissue sections sourced from the Department of Histopathology in a tertiary care cancer center. MATERIALS AND METHODS: Non-isotopic in situ hybridization (NISH) was performed on lymph node sections from 40 formalin-fixed paraffin-embedded tissues of DLBCLs using a digoxigenin-labeled HBVS gene probe. All patients were incidentally HBsAg negative. RESULTS: Eleven of the 40 lymph nodes from DLBCL patients were HBV NISH positive. However, the positive signals were non-uniformly distributed mainly in the nucleus of the large malignant lymphoid cells, despite all cases being seronegative for HBsAg. CONCLUSION: Nearly 28% of the patients' lymph nodes showed evidence of HBV DNA. A possible explanation for NISH positivity in seronegative DLBCLs could be due to occult HBV infection. Future studies on HBsAg seropositive and seronegative DLBCL cases using more sensitive assays like polymerase chain reaction ISH may elucidate the causal association of HBV with DLBCLs more precisely and define the magnitude of the association.