The new and reproducible Papanicolaou stain. Morphologic and spectrophotometric observations on the influence of stain composition on staining results.

The morphologic and spectroscopic characteristics of a new and reproducible modification of the Papanicolaou stain are briefly described. The main features of this modification are (1) replacement of the natural dye hematoxylin by the synthetic and chemically well defined dye thionin, (2) introduction of an alcoholic counterstain consisting of eosin gamma and fast green FCF only and (3) employment of alcoholic solutions only. The absorption characteristics of hematoxylin and thionin bound to chromatin are influenced by the cytoplasmic counterstaining, especially by the two green dyes, the absorption peaks of which are close to those of the nuclear stains. The implications of these results for visual and automated cytologic diagnosis are briefly discussed.