t(9;22)
An abnormal chromosome 22 that results from the Philadelphia translocation, a chromosomal translocation in which chromosomes 9 and 22 exchange a portion of their q arms. The Philadelphia chromosome produces the BCR-ABL1 fusion protein, which elevates tyrosine kinase enzyme activity. It is also referred to as t(9;22)(q34;q11.2). The translocation is implicated in the pathogenesis of several leukemias, most notably chronic myelogenous leukemia (CML).