Papanicolaou stain

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Papanicolaou stain
Stain in short

Low grade squamous intraepithelial lesion.
Abbreviation Pap stain
Similar stains Romanowsky stains
Use the standard stain in cytopathology
Interpretation blue/purple = nucleus, pink/green = cytoplasm, orange = keratin

Papanicolaou stain, abbreviated Pap stain, is a standard stain used in cytopathology.[1] It is a modified H&E stain.


  • Can be thought of as the H&E of cytopathology.
  • Specimens are fixed in ethanol.
  • Good for seeing nuclear detail.[1]
  • Out-of-focus cytoplasm is translucent; allows one to focus overlapped cells in different planes.



  • Blue/purple = nucleus.
  • Green/pink = cytoplasm.
  • Orange = keratin.


See also


  1. 1.0 1.1 Prabhudesai, NM.; Kulkarni, MB.; Desai, SB.; Borges, AM. (Jul 2004). "Modified H & E staining technique for fine needle aspiration cytology (FNAC) smears.". Indian J Pathol Microbiol 47 (3): 384-6. PMID 16295430.