Acute lymphoblastic leukemia with a hypodiploid karyotype with less than 40 chromosomes: the basis for division into two subgroups.

This paper describes seven patients with ALL and a hypodiploid karyotype with less than 40 chromosomes. A consideration of these and 15 previously published cases indicates that they may be divided into two groups depending on chromosome number, i.e., less than 30 and 30-39. The less than 30 group are younger and predominantly female when compared with the 30-39 group, who are generally older than 40 years and mainly male. In addition, the two groups show different characteristic patterns of chromosome loss. Morphologically, both groups have populations of large and small lymphoblasts containing numerous small vacuoles, and both have common ALL antigen phenotypes. We present the possibility that the ALL patients in the less than 30 group are an example of an age restricted leukemia. There is insufficient data to assess any prognostic differences between the two patient groupings.