Clonal characteristics of posttransplant lymphoproliferative disorders.

C LRRE~T MODELS of neoplasia indicate a stepwise serie5 of events as the usual mechanism b~ which normal cells become neoplastic cells. I However, ca ncer clinically presents as a full~ malignant lesion capable of causing the death of the host. For this reason, it is presently not possible to trace the entire process that led to this conditIon. The occurrence of lymph0proliferati vc disorders in immunosuppressed transplant recipients holds significant promise that a model of the early stages of neopbsia might exist in humans. These lesions. originally interpreted as .non-Hodgkin's lymphomas. occur in association with Epstein-Barr virus infection in most cases." Both pol~clonal and monoclonal forms have been described_'~ We previously observed that a significant number of posttransplant Iymphoproliferative disorders (PTLDs) seen in association with cyclosporine A(CsA)-steroid immunosup-pression were capable of regression after a reduction of immunosuppression. H Our continuing studies are designed to explore the limits of this phenomenon and define the host:tumor factors that are operative within this system. The present report describes a retrospective clonal analysis of tumor tissues by using recombinant D'A From Ihe Depanf?1tnlJ of Palhologl and Slirge'.I. fresbl'lerran ["nin'rslt! HMplla.