Background It is special because it is not a routine stain that is performed on a tissue sample. This stain has stood the test of time for nearly the entire 20th century. Hematoxylin stains tissue a deep blue while eosin stains a deep red. Depending upon the tissue, all cells are composed of a nearly infinite combination of the various hues and shades of these two stains.
Most cells have a reproducible staining pattern, regardless of the tissue.
The term usual is used to distinguish it from immunoperoxidase stains. These stains are not monoclonal antibodies and thus are not as specific for the tissue it stains. Nontheless, for many years, this panel of stains aided pathologists in diagnoses. A common stain is the mucicarmine stain which highlights mucin a bright pink on a background of yellow. The presence of mucin within a malignant tumor may indicate glandular differentiation suggesting it is an adenocarcinoma.