Pyothorax-associated lymphoma: EBV-positive lymphoma developing in immunocompetent patients

Malignant lymphomas frequently develop in the pleural cavity of patients with long-standing pyothorax. Thus, the term pyothorax-associated lymphoma (PAL) has been proposed for this type of tumor. Most of PALs are diffuse lymphomas of B cell type and contain Epstein-Barr virus (EBV) DNA. We established two lymphoma cell lines from biopsy specimens of PAL cases, and examined their growth characteristics and the expression of EBV latent infection genes and oncogenes. The differences in growth rate and oncogene expression between the lines could not be adequately explained by the pattern of EBV latent gene expression. The subsequent genetic lesions might be necessary for the development of overt lymphoma. Furthermore, the mechanism of development of viral antigen-positive tumor in immunocompetent patients is discussed.