Post-transplant lymphoma occurs due to proliferation of which of the following cells -

Post-transplant lymphoproliferative disorders (PTLD) are a diverse group of abnormal lymphoid growths that include both hyperplasias and neoplasias. They have been divided into several general pathologic categories that have prognostic significance. These include early or hyperplastic PTLD, polymorphic PTLD, and lymphomatous or monomorphic PTLD. The majority of PTLDs are of B-cell origin and contain Epstein-Barr virus (EBV), however, PTLDs of T or NK cell origin have been described and late-arising EBV negative lymphoid tumors are becoming more frequently reported in this population.