Papanicolaou EA 65 Stain: Composition & Diagnostic Use in Cytology

Papanicolaou EA 65 (EA-65) Formulation

Composition (w/w):

• Ethanol: 50%
• Acetone: 32%
• Ether: 16%
• Dyes: Eosin Y, Light Green SF yellowish, Bismarck Brown Y (in specific ratios)
• Phosphotungstic acid (mordant)
• Acetic acid (pH adjustment)

Diagnostic Application

• Purpose: Counterstain in Papanicolaou (Pap) staining protocol (after Harris hematoxylin).
• Highlights: Cytoplasm (eosinophilic = pink/red), keratin (green/blue), superficial vs. intermediate cell maturation.
• Specimens: Cervical/vaginal smears, sputum, urine, FNA, effusions.
• Critical for: Detecting dysplasia, carcinoma in situ, invasive squamous/adenocarcinoma.

Protocol Context

1. Fixation (95% ethanol or spray fixative)
2. Harris hematoxylin (nuclear stain)
3. Acid alcohol differentiation
4. Bluing (Scott's tap water)
5. EA-65 (counterstain)
6. Dehydration, clearing, mounting

EA-65 provides transparent cytoplasmic detail essential for nuclear:cytoplasmic ratio assessment—the cornerstone of cytologic malignancy grading.