NOVEL LEUKEMIC LYMPHOMA WITH PROBABLE DERIVATION FROM IMMATURE STAGE OF NATURAL-KILLER (NK) LINEAGE IN AN AGED PATIENT

A 66-year-old male patient was admitted with dyspnea; physical examina tion revealed petechiae and systemic lymphadenopathy. Laboratory findi ngs showed leukemia. The blasts in the peripheral blood were negative for cytochemical myeloperoxidase, and had condensed nuclear chromatin with a nucleolus. The histological diagnosis of the biopsied neck lymp h node was lymphoblastic lymphoma. The leukemia cells expressed CD2, C D6, CD7, CD13(low), CD56, beta chain of IL-2 receptor(low) (IL-2R beta ), and HLA-DR antigens, but not other pan-T (CD5, CD3, CD4, and CD8); pan-B (CD10, CD19, CD20, and CD24); natural killer (NK) (CD16, CD57); or myeloid (CD33) antigens. Electronmicroscopy revealed convoluted nuc lei with conspicuous nucleoli and peripherally condensed heterochromat in. Membrane-bound granules containing an electron dense matrix were o bserved in the cytoplasm, indicating the NK cell nature of the neoplas tic cells. While terminal deoxynucleotidyl transferase (TdT) and cytop lasmic CD3 were not detected by immunofluorescence on fixed smears, No rthern blot analysis revealed the gene expression of CD3 epsilon, CD3 zeta, and TdT. Gene rearrangement analysis revealed that the beta, gam ma, and delta chains of T-cell receptor (TCR) and immunoglobulin heavy chain (IgH) were of germline genotype. While the overall interpretati on of the phenotype and genotype was difficult, the derivation of an i mmature stage of NK lineage was strongly suggested, based predominantl y on the electronmicroscopic features. Despite initially successful ch emotherapy, the patient died 14 months after initial presentation.