In an experiment, cell samples are collected from the bone marrow aspirates of patients who were diagnosed with lymphoproliferative disorders. Cytogenetic analyses are performed on these cells, and a subset of the cases is found to have the BCR-ABL fusion gene from the reciprocal translocation t (9;22) (q34;11). The presence of this gene results in increased tyrosine kinase activity. Patients with which of the following conditions are most likely to have this gene?

This is the Philadelphia chromosome, or Ph1, which is characteristic of patients with chronic myelogenous leukemia (CML). This karyotypic abnormality can be found using cytogenetic techniques, including fluorescence in situ hybridization (FISH). In the few cases that appear negative by karyotyping and by FISH, molecular analysis shows BCR-ABL rearrangements, and the tyrosine kinase activated via this fusion gene is the target of current therapy for CML. This rearrangement is considered a diagnostic criterion for CML. CML is a disease of pluripotent stem cells that affects all lineages, but the granulocytic precursors expand preferentially in the chronic phase. Acute promyelocytic leukemias often have the t (15;17) abnormality. Follicular lymphomas have a t (14;18) karyotypic abnormality involving the BCL2 gene. Hodgkin disease and myelomas usually do not have characteristic karyotypic abnormalities.