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Papanicolaou stain (also Papanicolaou's stain and Pap stain) is a multichromatic (multicolored) cytologicalstaining technique developed by George Papanicolaou in 1942.[1][2][3] The Papanicolaou stain is one of the most widely used stains in cytology,[1] where it is used to aid pathologists in making a diagnosis. Although most notable for its use in the detection of cervical cancer in the Pap test or Pap smear, it is also used to stain non-gynecological specimen preparations from a variety of bodily secretions and from small needle biopsies of organs and tissues.[4][5] Papanicolaou published three formulations of this stain in 1942, 1954, and 1960.[2]
The pap stain is not fully standardized and comes in several formulations, differing in the exact dyes used, their ratios, and the timing of the process.[2][1] Pap staining is usually associated with cytopathology in which loose cells are examined, but the stain has also been modified and used on tissue slices.[9]
The second staining solution (designated OG-6), contains Orange G in 95% ethyl alcohol with a small amount of phosphotungstic acid.[12][2] In the OG-6, the OG signifies Orange G, and the '6' denotes the concentration of phosphotungstic acid added; other variants are OG-5 and OG-8).[2]
The third staining solution is composed of three dyes, Eosin Y, Light Green SF yellowish, and Bismarck brown Y in 95% ethyl alcohol with a small amount of phosphotungstic acid and lithium carbonate.[12][2] This solution, designated EA, followed by a number that denotes the proportion of the dyes, other formulations include EA-36, EA-50, and EA-65.[2]
The counterstains are dissolved in 95% ethyl alcohol which prevents cells from over staining which would obscure nuclear detail and cell outlines especially in the case when cells are overlapping on the slide.[3][2] Phosphotungstic acid is added to adjust the pH of counterstains and helps to optimize the color intensity.[2] The EA counterstain contains Bismarck brown and phosphotungstic acid, which when in combination, cause both to precipitate out of solution, reducing the useful life of the mixture.[2]
The stain should result in cells that are fairly transparent so even thicker specimens with overlapping cells can be interpreted.[2] Cell nuclei should be crisp, blue to black in color[12][13] and the chromatin patterns of the nucleus should be well defined. Cell cytoplasm stains blue-green and keratin stains orange in color.[13][5]
Ultrafast Papanicolaou stain is an alternative for the fine needle aspiration samples, developed to achieve comparable visual clarity in a significantly shorter time. The process differs in rehydration of the air-dried smear with saline, use 4% formaldehyde in 65% ethanolfixative, and use of Richard-Allan Hematoxylin-2 and Cyto-Stain, resulting in a 90-second process yielding transparent polychromatic stains.[15]
^ abRoss, Michael H.; Pawlina, Wojciech (2016). Histology : a text and atlas : with correlated cell and molecular biology (7th ed.). Wolters Kluwer. pp. 984p. ISBN978-1451187427.
^Yang GC, Alvarez II (1995). "Ultrafast Papanicolaou stain. An alternative preparation for fine needle aspiration cytology". Acta Cytol. 39 (1): 55–60. PMID7531380.
^Demay, Richard (2012). "Chapter 26: Stains". The art and science of cytopathology. Chicago, IL: Am Soc Clinical Pathology. p. 1505. ISBN978-0-89189-644-9. OCLC761848930.