THEORY AND PRACTICE OF SILVER STAINING IN HISTOPATHOLOGY

The special stains that utilize silver include various staining proced ures that are based on very different principles. Five categories of s ilver stains can be defined by the physicochemical procedures involved . These are argentaffin methods, argyrophil methods, impregnation stai ns, silver oxidation-reduction stains, and metallic-metallic interacti ons (autometallography). For example, neuroendocrine cells can be iden tified by argentaffin or argyrophil techniques; whereas axons, neurofi brillary tangles, and senile placques are identified by silver impregn ation techniques. Impregnation silver stains also can be used to demon strate bacteria that are difficult to stain by other methods or to cul ture. Fungi, basement membranes, and reticulum can be stained with pro cedures in which oxidation of carbohydrates and glycoproteins is follo wed by reduction of silver by the oxidized molecule. The general princ iples underlying these silver staining techniques and their effective use are described in this manuscript.