The colloidal iron stain with Prussian blue is a histological staining technique that is used to detect the presence of iron in tissues. The stain is commonly used in the diagnosis of iron overload disorders such as hemochromatosis.
Prussian blue is a blue-colored pigment that is produced when potassium ferricyanide and hydrochloric acid react with iron. In the context of the colloidal iron stain, Prussian blue appears as blue granules within the tissue sample, indicating the presence of iron.
The tissue section is then counterstained, which stains the nuclei of cells a different color from the Prussian blue granules. This allows for the visualization of the iron deposits within the tissue in contrast to the cell nuclei.