Cytogenetic characterization of natural killer cell leukemia.

Natural killer (NK) cell neoplasms are rare neoplasms characterized by cells with NK characteristics. Few descriptions of the karyotype of this tumor are available. We describe a case with sequential analysis of the karyotype over a 3-month period. Cytogenetic analyses performed on specimens from the patient's peripheral blood and bone marrow generated similar results. Karyotype of the unstimulated peripheral blood at diagnosis was 46,XX,i(7)(q10),der(17)t(1;17)(q21;p11.1),-18,+mar[15]. Notably, a single cell with only an i(7q) was found, suggesting that this was the primary chromosomal abnormality in the neoplasm. The second specimen, 2 weeks later, was from bone marrow. Both the i(7q) and der(17) were present in two clones, which differed from each other in having two distinct derivative chromosomes 10. In one clone, the additional material on the short arm of chromosome 10 appears to have originated from either chromosome 1p or chromosome 22q, whereas for the second clone the donor of the additional material is most likely chromosome 8q. Thus, the karyotype for the bone marrow specimen is 46,XX,i(7)(q10),add(10)(p11.2),der(17)t(1;17)(q21;p11.1)[8]/46,XX,i(7)(q10),der(10)t(8;10)(q21;p12),der(17)t(1;17)(q21;p11.1)[3]/46,XX[14]. A final bone marrow specimen, after chemotherapy and shortly before the patient's death, showed abnormalities similar to those identified previously. The abnormalities seen in chromosomes 7 and 17 are consistent with previous reports of chromosomal abnormalities in NK-cell lymphomas.