Background: Polymorphic reticulosis is one of several diseases constituting lethal midline granuloma (LMG). Previous immunohistochemical studies suggested a T-cell nature of proliferating cells; the term nasal T-cell lymphoma (NTL-LMG) has since been used widely. The authors' previous study in Asian countries showed the clustering of Mongolian patients with NTL-LMG, but the frequency varied with geographic area; it was much higher in Korea and southwest Japan (Okinawa) than in Shanghai and Honshu, Japan. Recently an etiologic role of Epstein-Barr virus (EBV) for the development of NTL-LMG has been postulated.
Methods: In this study, the presence of EBV and human T-cell lymphocytic leukemia virus type 1 (HTLV-1) genomes were examined in NTL-LMG patients from Southwest Japan (Okinawa, 10 patients), another Japanese district (Honshu, 21 patients), and Shanghai, China (5 patients). All of the tissues from different geographic sites were analyzed at one central location.
Results: Immunohistochemistry showed that proliferating large cells were positive for CD43 and/or CD45RO, identical with reported NTL-LMG cases. Polymerase chain reaction (PCR) revealed the presence of EBV genome in the NTL-LMG lesions, but the frequency varied according to the geographic area: 67% in Okinawa, 33% in Honshu, and 100% in Shanghai. In situ hybridization provided positive signals in the nuclei of proliferating cells. Expression of latent membrane protein in the proliferating cells of cases positive for EBV by PCR and in situ hybridization was confirmed.
Conclusions: The results suggest that the EBV may play a role in the development of NTL-LMG. However, the variation of frequency of EBV genome in different geographic locations suggests that EBV infection may not be an indispensable condition for the disease.