Clinical and Experimental Features of Natural Killer Cell Leukemias in a Chinese Population: A Single Center Experience of 10 Years

Abstract 4892

Leukemia of natural killer (NK) cell lineage is rare which affects Asian population preferentially. Here 10 Chinese patients with NK cell leukemia were retrospectively evaluated. Among them 7 man and 3 women, the middle age was 47 years (range 22–57 years). Aggressive NK cell leukemias were finally diagnosed in 7 patients, myeloid/NK cell precursor acute leukemias in 2 patients and NK-CLPD in 1 patient. Pronounced extramedullary involvements (breast mass, multiple subcutaneous nodes and eye rectus muscle mass) were the main manifestation in 2 myeloid/NK cell precursor acute leukemias and 1 aggressive NK-cell leukemia. Clonal cytogenetic abnormality (46, XX, 16P-) was only found in 1 myeloid/NK cell precursor acute leukemia patient. Epstein-Barr virus test was performed in 8 patients and 3 were Positive (all were aggressive NK-cell leukemias). The overall survival of 4 cases of aggressive NK-cell leukemias combined with hematophagocytic syndrome were less than 1.3 months. During following up, 8 patients died of disease, 1 NK-CLPD patient and 1 aggressive NK-cell leukemia patient treated by allo-BMT were still alive. The former NK-CLPD, who was in indolent course, survived 60+ months. The later patient was first diagnosed as NK-CLPD but with lymphoadenopathy and splenomegaly, the metabolic activity of spleen by F-18 FDG uptake was in normal range, lymph node pathology showed reactive change and PB EBV-DNA copy was negative, later hematophagocytic syndrome occurred and EBV-DNA copy became positive. The lymph node pathology were reexamined by FISH method and scattered EBV positive cells were found, so the exact diagnosis from beginning should be occult aggressive NK cell leukemia, soon matched sibling donor BMT was performed and the patient got complete remission and the EBV-DNA copy became negative and lived well for 10⁺ months. Natural killer cell neoplasms are rare and most in aggressive clinical course, novel therapeutic regimens including allogeneic bone marrow transplantation should be investigated to improve outcome of this disease.