Novel SSBP2‐JAK2 fusion gene resulting from a t(5;9)(q14.1;p24.1) in pre‐B acute lymphocytic leukemia

Activating mutations in JAK2 are found in virtually all patients with polycythemia vera, and about half of those with essential thrombocythemia and primary myelofibrosis. In addition, less common aberrations (particularly gene fusions) involving JAK2 have been described in acute leukemias. With the advent of JAK2 inhibitor trials in myeloproliferative disorders, tumors with JAK2 mutations or rearrangements have become candidates for targeted therapy. In this report, we identify SSBP2 as a new JAK2 fusion partner in a patient with pre-B cell acute lymphocytic leukemia. This finding adds to the expanding compendium of JAK2 aberrations found in various hematopoietic malignancies, as well as the potential need for a diagnostic FISH analysis in the appropriate clinical setting.