A 50-year-old man presents with progressive fatigue, early satiety, and a feeling of abdominal fullness. Physical examination reveals marked splenomegaly. Laboratory studies show leukocytosis (WBC 120,000/µL) with a left shift, normocytic anemia, thrombocytosis, and a very low leukocyte alkaline phosphatase (LAP) score. Genetic testing is most likely to reveal which of the following?
✓ Correct Answer: Option B
The constellation of marked leukocytosis with a left shift, splenomegaly, very low LAP score, and constitutional symptoms is highly suggestive of Chronic Myeloid Leukemia (CML). CML is characterized by the Philadelphia chromosome (t(9;22)), which results in the BCR-ABL fusion gene.