A 62-year-old man reports early satiety, fatigue, and generally feeling unwell. The symptoms started gradually and are getting worse. He notes no chest discomfort, respiratory symptoms, or abdominal pain.On physical examination, he appears pale, the vital signs are normal, and the pertinent findings are a large spleen, absence of lymph nodes, and normal heart and lung.His blood count is abnormal; the WBC is 50,000/mL with increased mature granulocytes, hemoglobin is 9.5 g/dL, and platelets are 450,000/mL. Which of the following cytogenetic changes is most characteristic of his condition?
High-Yield Explanation
This is a case of chronic myelogenous leukemia (CML). The reciprocal translocation involves the long arms of 22 and 9, and results in translocation of the ABL proto-oncogene from chromosome 9 adjacent to a portion of the BCR gene on chromosome 22. The resultant abnormal chromosome 22 is known as the Philadelphia (Phi) chromosome.