POSTTRANSPLANT LYMPHOPROLIFERATIVE DISORDERS WITH GENETIC ABNORMALITIES COMMONLY FOUND IN MALIGNANT-TUMORS

Post-transplant lymphoproliferative disorders (PTLD) are potentially f atal complications of organ transplants. Impairment of the immune syst em by immunosuppressive drugs is the assumed cause of PTLD. The Epstei n-Barr virus (EBV) is detected in most of the PTLD studied and is cons idered as the main aetiological agent. The clinical course of PTLD pat ients remains unpredictable, some lymphoproliferations regress after d iscontinuation of the immunosuppressive treatment, others behave as tr ue malignant tumours. The mechanism by which a viro-induced lymphoprol iferation evolves to an autonomous tumour remains unclear, and little is known about the genetic changes that occur during this process. We report two cases of fatal EBV-associated PTLD in heart transplant reci pients. Both tumours were monoclonal and carried numerous chromosomal abnormalities, including a classic t(8;14)(q24;q32) with rearrangement of the MYC proto-oncogene. One tumour demonstrated an amplification o f the proto-oncogene N-MYC. The EBNA2 gene was not expressed in tumora l cells, suggesting that the chromosomal abnormalities contributed the function of EBNA2 in these cells. The morphology of the tumours indic ated that the cases presented here were not Burkitt's lymphomas. These findings provide some clues with regard to the genetic changes which lead to a B-cell malignancy in some transplant patients.