Chapter 15: Molecular Applications

Much of routine pathologic examination of specimens still utilizes histochemical stains to distinguish different tissue types, which otherwise have limited contrast in brightfield microscopy. In general, these stains rely on differences in the organization of macromolecules in tissues, and their interactions with dyes through various modes of chemical bonding. In particular, these dyes are directed to their potential binding sites by electrostatic forces generated from the manipulation of solvent during the staining process, and actual binding of the dye to tissues (i.e. “staining”) typically occurs through other forces such as hydrophobic interaction. Given the relatively non-specific nature of traditional histochemical methods, immunohistochemistry or in situ hybridization are routinely used to obtain more specific staining for a particular protein or nucleic acid…