Traditional staining for routine diagnostic pathology including the role of tannic acid. 1. Value and limitations of the hematoxylin-eosin stain

The components of the hematoxylin and eosin (H & E) stain (i.e. hemalum and eosin Y), their contributions to the typical staining pattern, and the reasons why the H & E stains are the preferred oversight stains for routine diagnostic histopathology are discussed. The essential diagnostic significance of effective nuclear staining by hemalum, providing information on nuclear morphology and texture, is emphasized; as is the ironic advantage for routine diagnostic histopathology of the limited range of colors provided by H & E staining, that allows recognition of significant features under low microscopic magnifications. Standardization of hemalum is considered, along with probable reasons why users show resistance to such a concept. Counterstaining with anionic (acid) dyes is discussed, as is the important phenomenon of contrast. The particular advantages and disadvantages of eosin Y and phloxin B as counterstains to hemalum are outlined. The concept of an “ideal routine histological stain” is considered, and H & E is compared to such an ideal case. Finally, deficiencies of H & E staining are discussed, and a program to develop an improved oversight stain is introduced.