Background and objectives: Extranodal NK/T-cell lymphoma, nasal type is an aggressive lymphoma that is always associated with Epstein-Barr virus (EBV). This study was done to evaluate the use of EBV-encoded RNA-1 in situ hybridization (EBER-1 ISH) to detect occult micrometastasis in the bone marrow (BM) of patients with nasal NK/T-cell lymphoma.
Design and methods: A total of 23 patients who underwent BM biopsy for routine pre-therapeutic evaluation were enrolled in the study. We used EBER-1 ISH to investigate the expression of EBER-1 in 30 BM specimens. The clinical correlation and therapeutic outcomes of these patients were analyzed. In addition, genomic analysis of EBV was performed in five patients.
Results: Conventional morphologic examinations failed to identify any lymphoma involvement in the 23 BM specimens obtained at initial staging. However, 10 of the 23 BM were positive for EBER-1. A lower survival rate was seen in patients with BM positive for EBER-1. Only the BM EBER-1 ISH result was shown to be an independent variable predicting overall survival in stage I and II patients (p=0.027; hazard ratio for death 0.066, 95% confidence interval, 0.006 to 0.733), suggesting that EBER-1 positivity in BM is the major determinant of a poor prognosis. However, discrepancies in the EBV strains between the primary tumor and BM existed in two of the five studied patients.
Interpretation and conclusions: We suggest that EBER-1 ISH should be performed on BM specimens of patients with nasal NK/T-cell lymphoma to identify the presence of EBER-1 positive cells, which appears to carry a poor prognosis. Whether or not the EBER-1 positive cells in the BM of nasal NK/T-cell lymphoma patients are true tumor cells requires further study.