Posttransplant Lymphoproliferative Disorders:Immunohistologic Differential Diagnosis With Severe Allograft Rejection

Posttransplant lymphoproliferative disorders (PTLD) are an acknowledged complica tion of transplantation and immunosuppression that may be difficult to distinguish from severe rejection in small biopsy specimens. In this study we compared 19 exam ples of PTLD with 20 cases of severe rejection. Antibodies to CD20, CD43, CD45, CD45RO, MB2, Epstein-Barr virus-latent membrane protein, bcl-2, proliferating cell nuclear antigen, cytomegalovirus early antigen, and hepatitis B surface and core anti gens were employed. The results expressed as percentage of positive cases of PTLD/ rejection, were: CD20, 89/0; CD43, 63/100; CD45, 100/100; CD45RO, 5/85; MB2, 32/0; Epstein-Barr virus-latent membrane protein, 79/0. Aberrant coexpression of CD20 and CD43 was seen in 11 cases of PTLD and no cases of severe rejection. The proliferating cell nuclear antigen index was 58% in PTLD cases, and 20% in rejection; stains for bcl-2 protein were nondiscriminatory. No examples of either process were reactive for cytomegalovirus or hepatitis B antigens. These results indicate that PTLD usually has a B-cell phenotype, often with associated necrosis, while acute rejection is a T-cell process. Expression of Epstein-Barr virus-latent membrane protein, and coexpression of CD43 and CD20 are additional attributes of PTLD. Int J Surg Pathol 2(2):105-116, 1994