Sideroblasts

Definition:
Sideroblasts are normoblasts of bone marrow which contain fine hemosiderin granula demonstrated by the iron stain. They constitute at most 4% of the normoblasts.

Appearance:
Sideroblasts must be differentiated from ringed sideroblasts, which occur in sideroachrestic disorders. In sideroblasts the iron is located in the cytoplasm. This is why the blue stained granules are diffusely scattered over the whole cell. In the case of ringed sideroblasts, the iron is in the mitochondria which are arranged around the nucleus. The granules are coarse in ringed sideroblasts.