Prussian Blue stain is used to detect which form of iron in tissue?

• A. Ferric iron
• B. Ferrous iron
• C. Metallic iron
• D. Iron oxide

Answer: (A)

Prussian Blue staining targets ferric iron (Fe3+) in tissue. The chemical reaction uses potassium ferrocyanide to react with ferric iron to form ferric ferrocyanide, the blue pigment known as Prussian blue. This means iron stored in ferritin or hemosiderin, which is in the ferric form, appears as blue deposits under the microscope. Ferrous iron (Fe2+) does not form the blue complex, and metallic iron or iron oxide particles are not detected by this stain. So the best answer is ferric iron.