T-CELL RICH, KI-1-POSITIVE POSTTRANSPLANT LYMPHOPROLIFERATIVE DISORDER - A PREVIOUSLY UNDESCRIBED VARIANT FOLLOWING LIVER-TRANSPLANT

Post-transplant lymphoproliferative disorders (PTLD) are a consequence of the immunosuppressive therapy following organ transplant. We descr ibe a patient who developed PTLD seven years after liver transplant an d while receiving cyclosporine and prednisone, Magnetic resonance imag ing demonstrated a paraspinal mass extending from T11 to LI. Microscop ically, this was composed of a diffuse infiltrate of small to intermed iate sized T-lymphocytes with clusters of large anaplastic tumor cells with amphophilic cytoplasm, large irregular nuclei and prominent nucl eoli. A high mitotic rate and atypical mitotic figures were noted in t he clusters of large cells. Flow cytometric and immunohistochemical an alysis failed to identify either a monoclonal B-cell population or a T -cell population with aberrant expression of the T-cell surface marker s. Strong positivity for CD30 and focal staining for epithelial membra ne antigen (EMA) of the large cells was seen. Leukocyte common antigen (LCA), cytokeratin, vimentin, monocyte/macrophage and B- and T-marker s were negative. The small lymphoid cells were positive for CD3, MT-I and UCHL-1. Based on the immunophenotypic and morphological evaluation , this was characterized as a T-cell rich PTLD. PCR analysis identifie d a monoclonal population of B-cells. This unusual case emphasizes the morphological and immunophenotypic diversity of PTLD. The utility of PCR analysis in the evaluation of PTLD Is also demonstrated.