Acute lymphoblastic leukemia supervening in a case of chronic lymphocytic leukemia after continuous 3-year treatment with chlorambucil

A case is presented of a patient with classical chronic lymphatic leukemia (CLL) treated with continuous chlorambucil for 3 years who presented with a picture of acute leukemia. The peripheral blood still showed a prevalence of mature lymphocytes with a few blast cells, whereas the bone marrow showed a predominant population of blast cells possessing a null acute lymphoblastic leukemia phenotype. Karyotype analysis showed a prevalent hyperdiploid clone of 67 to 68 chromosomes with endoreduplication and marker chromosomes. The coexistence of a CLL-type population with the blastic, undifferentiated cell clone suggests a second malignancy superimposed on the previous leukemic process, and possibly brought about by the continuous chlorambucil treatment.