Evidence for local immunosuppression and demonstration of c-myc amplification in pyothorax-associated lymphoma

Pyothorax-associated lymphoma (PAL) develops in the pleural cavity of patients with a long history of pyothorax. Epstein-Barr virus (EBV) is also involved in PAL, similar to lymphomas in immunodeficient patients. Here we examined T-lymphocyte subsets as well as c-myc and REL gene amplification in PAL tissues.We determined the number and distribution of CD4+ and CD8+ T-lymphocytes, to evaluate T-cells in the host immune reaction in seven cases of PAL. As controls, we also studied 10 cases of extranodal diffuse large B-cell lymphoma (DLBL) and 10 cases of nodal DLBL. Chromosomal imbalances in PAL were determined by using comparative genomic hybridization (CGH) analysis. The mean numbers of CD4+ and CD8+ and their ratio were significantly lower in PAL than in nodal DLBL. CGH analysis of PAL showed amplification of the 8q24 chromosomal region. In addition, c-myc amplification was found in four cases of PAL by Southern blot analysis.Our results suggest that the development of PAL may involve a local immunosuppressive environment and that amplification of c-myc might promote tumour progression, as has been described in the development of Burkitt's lymphoma.