Leukemia is a cancer of which blood cells?

• A. Red blood cells
• B. Platelets
• C. Plasma
• D. White blood cells

Answer: (D)

The main idea here is understanding which blood cells become cancerous in leukemia. Leukemia is a cancer of white blood cells, meaning abnormal white blood cell precursors multiply uncontrollably in the bone marrow and spill into the blood. These malignant cells disrupt normal blood formation, which can lead to infections (from dysfunctional or crowded immune cells), fatigue (from reduced red cells), and easy bruising (from low platelets). Red blood cells are the cells that carry oxygen, and platelets help with clotting; leukemia isn’t a cancer of those cells. Plasma is the fluid component of blood, not a cellular component. So the best answer is white blood cells.