Posttransplant lymphoproliferative disorder (PTLD) typically presents with either polymorphic or monomorphic histology. While both are the end result of immunosuppressive therapies, their origins are felt to be different with different prognoses and responsiveness to therapy, resulting in 2 different malignancies. We attempted to confirm reports suggesting that the relative frequency of these 2 histologies is shifting over time. We analyzed 3040 adult PTLD cases in the UNOS OPTN database from 1999 to 2013. Changes in PTLD cases over time were analyzed for histology, time from transplant to diagnosis, and patient EBV serostatus. We found that the relative proportion of polymorphic versus monomorphic histology has changed with an increase in the proportion of monomorphic cases with time (1999-2003, 54.9% vs. 45.1%; 2004-2008, 58.3% vs. 41.7%; 2009-2013, 69.7% vs. 30.3%; P = <.001). The change is driven by a gradual increase in the number of monomorphic PTLD with a steady number of polymorphic PTLD. The change is most strongly seen in transplant recipients who were EBV serostatus positive at the time of transplant. Potential causes are changes in immunosuppressive regimens with increased tacrolimus use (P = .009) and increased survival among transplant patients leading to later occurrence of PTLD (P = .001) that have occurred during the time frame analyzed. As organ transplantation has evolved over time, PTLD has coevolved. These changes in histology have important implications regarding the origin and clinical management of PTLD.
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