Stain used for degenerated fungi in tissue is
**Core Concept**
The question is testing the knowledge of histopathological staining techniques used to identify degenerated fungi in tissue samples. This involves the use of specific dyes that bind to fungal elements, allowing for their visualization under a microscope.
**Why the Correct Answer is Right**
The correct answer is Grocott's methenamine silver (GMS) stain. GMS stain is a widely used method for detecting fungi, especially in tissue samples. The stain works by binding to the polysaccharide components of fungal cell walls, such as chitin and glucans, which are resistant to degradation. This results in a black precipitate that can be seen under a microscope, allowing for the identification of fungal elements. The mechanism of GMS stain is based on the reduction of methenamine to formaldehyde by silver ions, which then reacts with the polysaccharides in the fungal cell walls.
**Why Each Wrong Option is Incorrect**
**Option A:** H&E stain is a general-purpose stain used for histopathological examination, but it is not specific for detecting fungi.
**Option B:** Periodic acid-Schiff (PAS) stain is used to detect carbohydrates, such as glycogen and mucin, but it is not specific for fungi.
**Option C:** Alcian blue stain is used to detect acidic mucins, but it is not used for detecting fungi.
**Clinical Pearl / High-Yield Fact**
GMS stain is a sensitive and specific method for detecting fungi, especially in tissue samples. It is an essential tool in the diagnosis of fungal infections, such as histoplasmosis and cryptococcosis.
**Correct Answer:** C. GMS.