Kidney allograft with a lymphocytic infiltrate: acute rejection, posttransplantation lymphoproliferative disorder, neither, or both entities?

The two cases presented illustrate the diagnostic difficulties and recommend an approach to use in patients in whom features of acute renal allograft rejection and posttransplant lymphoproliferative disorder (PTLD) appear simultaneously in allograft biopsies. Both patients developed acute allograft rejection episodes in the early post-transplant period followed by severe immunosuppression (OKT-3) and active Epstein-Barr virus infection. In addition to early recognition of light microscopic features of PTLD, immunohistology and in situ hybridization for EBV complement the diagnostic work-up and provide clues to the prompt diagnosis of rapidly developing PTLD affecting the allograft even in the face of persisting rejection.