state the principle and methodology of pearls pussian blue reaction in histopathology

The Prussian blue reaction, also known as Perls' Prussian Blue stain, is a histological stain used to detect the presence of iron in tissue samples.

Principle: The principle behind the Perls' Prussian Blue reaction is the formation of a bright blue pigment called "Prussian blue" when tissue iron reacts with potassium ferrocyanide in the presence of hydrochloric acid. This reaction specifically identifies ferric iron (Fe3+).

Methodology:

1. The tissue sample is first deparaffinized and hydrated to water.
2. The sample is then treated with a mixture of equal parts of 20% hydrochloric acid and 10% potassium ferrocyanide for 20 minutes. This is the Perls' reagent.
3. The sample is rinsed in distilled water.
4. The sample is then counterstained with nuclear fast red for 5 minutes. This stains the nuclei and provides a contrast to the blue of the Prussian blue reaction.
5. The sample is rinsed in distilled water, dehydrated, cleared, and mounted.

The presence of blue staining indicates the presence of ferric iron. This technique is commonly used to identify iron in cases of iron overload, such as hemochromatosis, and to identify the mineralized deposits in diseases like hemosiderosis.