Diagnosis. The diagnosis of PTLD requires a tissue biopsy, evaluation of histopathological morphology, immunophenotype, presence of clonality, and testing for EBV. The WHO classification of tumors of hematopoietic and lymphoid tissues lists early lesions, PTLD, monomorphic PTLD including B and T cell tumors, and classical Hodgkin's disease. Early lesions, including infectious mononucleosis-like hyperplasia, are considered