Sideroblasts are erythroblasts (immature red blood cells) in the bone marrow that contain granules of iron that have not been incorporated into hemoglobin. These iron granules are visible when the cells are stained with Prussian blue, a technique commonly used in histology to identify iron deposits. Sideroblasts are a normal part of erythropoiesis, the process of red blood cell formation, but they become significant in certain pathological conditions.
