5q - marker chromosome in acute leukemia with lymphoid morphology and myeloid differentiation antigens

We present three patients, two children and one adult, with an unusual type of acute leukemia. Whereas the blast cells showed lymphoid morphology with correlating cytochemical staining, immunological phenotyping showed a pure myeloid in one and a biphenotypic (mixed lymphoid/myeloid) membrane marker profile in two of the patients. Cytogenetic studies revealed a 5q - chromosome as a common marker with additional individual changes. Two of the patients who were treated according to ALL-therapy protocols died without remission 5 and 4 weeks after diagnosis, respectively. Despite relapsing several times, the third patient survived for over 8 years. These three patients seem to represent one new subgroup of leukemias which can only be distinguished from typical ALL by determination of both cell surface markers and cytogenetic analysis.