Assessment of Epstein-Barr virus association with pediatric non-hodgkin lymphoma in immunocompetent and in immunocompromised patients in Argentina. 
Epstein-Barr virus (EBV) has been classically associated with 3 malignancies, Burkitt lymphoma, B-cell lymphoproliferative syndromes, and nasopharyngeal carcinoma, and more recently with Hodgkin disease, T-cell lymphomas, and gastric and breast carcinomas, as well as with leiomyosarcoma and leiomyoma associated with immunosuppression.  To compare EBV expression in Argentine tumor samples with those reported elsewhere, we analyzed EBV expression in an Argentine pediatric population with non-Hodgkin lymphoma and correlated these results with clinical course and outcome.  We studied EBV presence by latent membrane protein-1 protein labeling by immunohistochemistry, by in situ hybridization, and by polymerase chain reaction for Epstein-Barr-encoded RNAs (EBERs) in formalin-fixed and paraffin-embedded non-Hodgkin lymphoma tissue samples (collected retrospectively) from 32 pediatric patients at Ricardo Gutiérrez Children's Hospital from 1993 to 2000.  Eight out of the 32 (25%) non-Hodgkin lymphoma cases showed latent membrane protein-1 and EBERs by in situ hybridization positive staining in tumor cells.  Among EBERs and latent membrane protein-1-positive cases, there were 5 immunocompromised patients, with either human immunodeficiency virus infection or primary immunodeficiency.  The EBERs in situ hybridization results were confirmed by EBERs polymerase chain reaction in good-quality DNA from 11 samples, with 3 proving positive and 8 negative.  The association of EBV with non-Hodgkin lymphoma in the Argentine pediatric population was low (25%), and this figure rose to 100% when only the immunocompromised patients subgroup was considered, confirming that the virus is probably a cofactor in the lymphomagenesis of some but not all pediatric non-Hodgkin lymphoma.  So far, no differences in clinical outcome are discernible between EBV-positive and EBV-negative non-Hodgkin lymphoma patients.