Canis ISSN: 2398-2942

Staining techniques: Papanicolaou stain

Synonym(s): Pap's

Contributor(s): Kathleen P Freeman, Karen Gerber

Introduction

  • Use two dyes that differ in their affinity for various sites within a cell, ie nucleus and cytoplasm. There is no chemical interaction between nuclear and cytoplasmic solutions (different to Romanowsky stains Staining techniques: Romanowsky-type stains ), they bind electrostatically, resulting in salt formation.
  • Papanicolaou stains are similar to Hematoxylin and Eosin, except that eosin is replaced with two cytoplasmic counterstains (that highlight keratinization in squamous epithelium).

Uses

  • Special diagnostic situations, in particular where neoplasia is suspected.
  • Excellent demonstration of nuclear and nucleolar changes.
  • Useful in thick smears and tissue fragments, particularly when nuclear detail is important (provides some architectural information for cytopathologists).

Advantages

  • Unique ability to highlight cytoplasmic keratin (orange to orange-red).

Disadvantages

  • Inferior cytoplasmic detail, secretory products in cytology and organisms (including bacteria) compared to Romanowsky stains.
  • Preparation must be wet - fixed, ie cells must be fixed before cells have dried, unless use modified Pananicolaou where smears are rehydrated.
  • Adhesive-coated slides (poly-l-lysine, gelatine) may aid cell retention.

Requirements

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Procedure

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • J√∂rundsson E , Lumsden J H & Jacobs R M (1999) Rapid Staining techniques in Cytopathology: A Review and Comparison of Modified protocols for Haematoxylin and Eosin, Papanicolaou and Romanowsky stains. Vet Clin Pathol 28 (3), 100-108 PubMed.

Other sources of information

  • Bibbo M (ed) (1997) Comprehensive Cytopathology. 2nd edn. W B Saunders, London. pp 889-917.
  • Pratt P W Laboratory Procedures For Veterinary Technicians. 3rd edn. Mosby. p 548.


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