Increased numbers of marrow basophils may be associated with a t(6;9) in ANLL.

We have characterized another subset of acute nonlymphocytic leukemia (ANLL) based on the cytogenetic and morphologic findings in a group of nine patients. Five patients had chromosomal analyses performed at the University of Chicago, two patients were studied at the All-Union Cancer Research Center in Moscow, and one patient each was studied at the University of Maryland and at Fairfax Hospital in Fairfax, Virginia. All nine patients had a reciprocal translocation involving the short arm of chromosome 6 and the long arm of chromosome 9 [t(6;9)(p23;q34)]. The patients, four males and five females, ranged in age from 5 to 51 years; the median age of 38 years is lower than that typically seen in ANLL. Only two of eight treated patients entered a complete remission. Classification of bone marrow morphology according to FAB Cooperative Group criteria revealed AML-M1 in one patient, AML-M2 in four, and AMMoL-M4 in three. One patient had refractory anemia with excess blasts (RAEB) which evolved to AML-M2. All bone marrow specimens showed severe myelodysplasia, with Auer rods present in seven of the nine cases. Of note was the particular prominence of bone marrow basophils (greater than 1%) in eight of the nine (89%) patients. Among 160 evaluable patients with ANLL de novo seen at the University of Chicago whose cells lacked a t(6;9), only five (3%) had greater than 1% basophils in the marrow aspirates. It is of interest that the breakpoint in 9q involves the same chromosomal band as that in the t(9;22) observed in chronic myelogenous leukemia (CML), in which increased basophils are a prominent feature. Thus, the association of the t(6;9) with increased bone marrow basophils in ANLL may provide additional insight into the chromosomal location of genes regulating the production and/or maturation of basophils.