Lapis ISSN 2398-2969

Staining technique: Papanicolaou

Synonym(s): Pap

Contributor(s): Molly Varga, Sarah Pellett

Introduction

  • Papanicolaou was originally associated with cervical screening, staining cervical cells in three stages with competing dyes.
  • The Papanicolaou stain is also used for clinical material and is normally used to stain bodily secretions, fine needle aspirates and touch preparations.
  • Two dyes are used that differ in their affinity for various sites within a cell, ie nucleus and cytoplasm.
  • Different to Romanowsky stains in that there is no chemical interaction between nuclear and cytoplasmic solutions. They bind electrostatically, resulting in salt formation.
  • Similar to hematoxylin and eosin, except that eosin is replaced with two cytoplasmic counterstains. This highlights keratinization in squamous epithelium.
  • The important elements of Papanicolaou staining methods are nuclear staining followed by orange and polychromic cytoplasmic staining (hematoxylin stain + orange stain + polychromic stain = Papanicolaou stain).
  • Using this method, cells are highly transparent allowing diagnosis, even when cells are overlapping and when mucus or inflammatory cells are present.
  • The staining method can be applied either manually with the aid of cuvettes, or mechanically in automated staining systems.

Requirements

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Procedure

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Further Reading

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