Which stain is commonly used for cytology smears?

• A. Papanicolaou
• B. Hematoxylin & Eosin
• C. Toluidine blue
• D. Masson's Trichrome

Answer: (A)

For cytology smears you want a stain that makes nuclear detail stand out and differentiates the various cytoplasm colors across exfoliated cells. The Papanicolaou stain is specifically designed for this purpose. It uses a sequence of dyes to produce crisp, blue‑black nuclei and a range of cytoplasmic colors, which enhances visualization of nuclear morphology, chromatin pattern, and cytoplasmic characteristics. This contrast is essential for identifying abnormalities in cytology specimens, especially in cervical cytology.

Other stains listed are not optimized for cytology smears. Hematoxylin & Eosin is a workhorse for tissue sections and doesn’t always provide the same cytoplasmic detail or multi-tone differentiation needed in smears. Toluidine blue is used for other purposes, such as mast cells or specific cytochemical applications. Masson's Trichrome targets connective tissue in histology.