Epstein–Barr virus (EBV)‐positive pyothorax‐associated lymphoma (PAL): chromosomal integration of EBV in a novel CD2‐positive PAL B‐cell line

Summary. Pyothorax‐associated lymphoma (PAL) is a clinico‐pathological entity arising in the pleural cavity of patients with long‐standing inflammatory pyothorax. PAL is closely associated with Epstein–Barr virus (EBV), but how this virus contributes to the development of the lymphoma is unknown. We have successfully obtained a novel EBV‐infected PAL cell line, designated Pal‐1. The cell line and its source coexpressed CD2 and CD20 molecules, but other representative B‐ and T‐cell markers such as CD1, CD3, CD5, CD7, CD10 and CD19 were not found. The B‐cell origin of Pal‐1 cells was proven by rearrangement of the immunoglobulin heavy‐ and light‐chain genes without rearranged T‐cell receptor genes. Both the cell line and primary tumour cells carried monoclonal EBV genome. Although EBV genome is known to be maintained as circular extrachromosomal DNA, neither circular nor linear extrachromosomal EBV DNA was detectable in Pal‐1 cells by in situ lysis gel analysis. Fluorescence in situ hybridization demonstrated viral integration at a marker chromosome mostly consisting of the centromere region of chromosome 1. The viral integration event may enhance a chromosomal instability at the insertion site. This cell line represents the first example of EBV integration in PAL and could enable the study of the potential role of integrated viral infection in the development of PAL as well as mechanism of the aberrant phenotype expression.