Grocott's methenamine silver stain

It can be used to identify the yeast-like fungus Pneumocystis jiroveci,[1] which causes a form of pneumonia called Pneumocystis pneumonia (PCP) or pneumocystosis.

The cell walls of these organisms are outlined by the brown to black stain.

The principle of GMS is the reduction of silver ions, which renders the fungal cell wall black.

The fungal cell wall commonly contains polysaccharides.

In a GMS procedure, chromic acid is first used to oxidize polysaccharides, generating aldehydes.

A small intestine sample stained using the Grocott's methenamine silver stain demonstrating histoplasma (black round yeast with narrow budding) in a granuloma