Epstein-Barr virus incidental expression in bone marrow cells: a study of 230 consecutive bone marrow biopsy samples

Epstein-Barr virus (EBV) is associated with many neoplastic hematologic conditions, but scattered EBV-positive cells can be detected in lymph nodes of healthy individuals and they usually represent latently infected lymphocytes. The incidence of EBV detection in normal bone marrow samples has not been studied and is largely unknown. The lack of knowledge regarding the true incidence of encountering bystander latent EBV-positive cells in the bone marrow may potentially lead to a diagnostic dilemma when assessing a staging bone marrow for a patient with an EBV-positive B or T/NK-cell lymphoma. The aim of our study was to investigate the rate of detection of EBV expression in bone marrow samples and correlate any positive findings with various clinical parameters including patient's age, sex, clinical history, immune status, and any neoplastic transformation if follow-up data are available. We retrospectively studied 230 consecutive bone marrow biopsies performed in 2013 and found 5 cases (2.17%) with scattered EBV-positive cells by in situ hybridization. The observed scattered EBV-positive cells are largely small in size and likely represent bystander, latently infected cells. The rate of detection of EBV-positive cells in the bone marrow appears to be slightly higher in immunodeficient individuals (3%) than in immunocompetent patients (1%).