Which stain stains cytoplasm of intermediate and parabasal cells?

• A. Harris hematoxylin
• B. EA 50 stain
• C. OG 6 stain
• D. Papanicolaou

Answer: (B)

Staining cytoplasmic maturation in Pap-stained smears relies on differential dye uptake by the cytoplasm of different cell types. The EA stain, which is Eosin Azure, is designed to color the cytoplasm of immature squamous cells—parabasal and intermediate cells—in a blue-green to blue-gray hue. The 50 in EA 50 refers to the concentration used, which optimizes contrast for these particular cells. Harris hematoxylin mainly stains nuclei, not the cytoplasm. OG 6 stains keratinized or keratin-rich cytoplasm orange, highlighting superficial cells rather than the immature ones. While the Papanicolaou method uses a combination of dyes to stain both nuclei and cytoplasm, it is the EA component that best distinguishes the cytoplasm of intermediate and parabasal cells. Hence, EA 50 is the stain that colors the cytoplasm of those cells.