5q- chromosome in acute leukemia with lymphoid morphology and expression of myeloid membrane determinants

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 exhibited a pure myeloid in one patient and a biphenotypic membrane marker profile in the other two patients. Cytogenetic studies revealed a 5q- chromosome as a common marker and additional individual changes. Two of the patients who were treated according to acute lymphoblastic leukemia (ALL) therapy protocols died without remission five and four weeks after diagnosis, respectively. Despite relapsing several times, another patient survived for over eight years. These three patients seem to represent one new subgroup of leukemias that can only be distinguished from typical ALL by both determination of cell surface markers and cytogenetic analysis.