Leukemia is best described as a cancer of which blood component?

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

Answer: (B)

Leukemia is a cancer of white blood cells. In this disease, the white blood cells—part of the immune system that should help fight infection—become abnormal and multiply uncontrollably in the bone marrow, often spilling into the bloodstream. Because the marrow is crowded with these cancerous cells, it makes fewer healthy red blood cells and platelets. That can lead to fatigue from anemia and a tendency to bruise or bleed easily due to low platelets, along with increased infections from dysfunctional immune cells. Plasma is the fluid component of blood, not a target of leukemia, and red blood cells or platelets aren’t cancers themselves, though their numbers can be affected. So, the condition is best described as a cancer of white blood cells.