Killer T-cell induction in patients with blastic natural killer cell lymphoma/leukaemia: implications for successful treatment and possible therapeutic strategies

A rare form of putative natural killer (NK) cell lymphoma called blastic NK cell lymphoma appears to be clinicopathologically distinctive in showing a homogenous lymphoblast, variable expression of CD2, CD4, CD56 and TdT, neg ative for surface CD3, T-cell receptor antigen, CD16, CD34 and lack of asso ciation with Epstein-Barr virus (EBV), We report two patients with blastic NK cell lymphoma and describe the interesting clinical studies. The patient s presented with cutaneous plaques. Both patients had adenopathy, and one h ad marrow involvement at presentation, Unlike in many NK and NK-like T-cell disorders, azurophilic cytoplasmic granules were absent. They expressed in termediate density CD45. In addition, the cells were positive for HLA-DR, C D2, CD4, CD56 and TdT, and negative for EBV transcripts, In spite of the ad vanced clinical stage, complete remission was achieved by conventional chem otherapy. After interleukin 2 expansion of tumour-infiltrating bone marrow and lymph node cells from the patients, cytotoxic T-cell lines with rearran ged T-cell receptor genes were established. They showed specific killing ac tivity against autologous tumour cells in an MHC-restricted fashion, with p ossible implications for treatment. In addition, upon cessation of maintena nce chemotherapy, one patient developed overt leukaemia with blasts express ing CD33 antigens, suggesting a continuous spectrum of blastic NK cell lymp homa to myeloid/NK cell precursor acute leukaemia.