ABSTRACT: Because histochemical staining is the principal means by which the biochemical information that this approach produces is converted to comprehensible visual data, it remains central to clinical pathology. While H&E staining provides a relatively simple morphological reference, the diagnostic utility of these has limited insights on what specific molecular features are represented and fails to accurately detect subtle architectural features such as mild fibrosis or basement membrane thickening. The transition from routine histopathology techniques to ancillary stains such as Periodic Acid–Schiff (PAS), Masson’s Trichrome and silver impregnation will be illustrated in this article. We focused here on the chemical logic behind these reactions ranging from outcomes of the oxidation mechanisms practiced by PAS to biological reduction met with metallic staining in silver stains, and modern use of immunohistochemistry (IHC) for diagnosis beyond a gross characterization. The classical specialized stains are “gold standards” as despite advances in genomic sequencing, they are both reproducible and cost-effective, providing the vital architectural context in assessing microbial infections and organ failure.
Keywords: Histochemical staining, PAS staining, Masson’s trichrome, silver stain, Immunohistochemistry; Pathological diagnosis