the use of formalin-based fixatives in cytology
Fixation means prevention of degeneration of cells and tissue by the autolytic enzymes present in the cells and preservation of cells as close as possible to the living state (Manual for Cytology, 2005). Specifically in cytology, the purpose of fixation is to
Maintain, as closely as possible, the cytomorphologic characteristics and diagnostically essential cytochemical elements of the cell. (Yoshida, 2004)
Deactivate autolytic enzymes
Replace cellular water
Facilitate diffusion of dyes across cell boundaries
Help cells adhere to a glass slide surface.
Stop cellular and microbial growth (anti-microbial). (Bibbo, 2008)
Whilst avoiding;
Excessively shrinking or swelling cells.
Distortion or dissolving of cellular components. (Manual for Cytology, 2005)
Common fixatives used in cytology include; alcoholic based fixatives such as 95% ethanol, coating fixatives such as Polyethylene glycol, special fixatives such as Carnoy’s fixative and finally formalin based fixatives such as alcoholic formalin and formalin vapour.
Formalin (4% formaldehyde) fixes tissue by cross-linking the proteins, primarily the residues of the basic amino acid lysine. Though it is widely used in histology as the optimally preferred fixative, its uses is somehow limited in cytology. This paper is to review some of merits and demerits of the its use in cytology how it has become unpopular.
MERITS
In a study conducted by Shivakumarswamy et al., 2012, the diagnostic utility of cell block preparation using 10% alcohol-formalin as a fixative was compared with the conventional smear. In this study it was concluded that the 10% alcoholic fixative is optimal for the cell block technique, in that, they got better cellularity as formalin minimized the cell loss by forming protein cross links and gel formation that could not be dissolved by various chemicals used for processing. And this contributed to the diagnosis of malignancies by the Cell Block methods, which were reported as negative in
Maintain, as closely as possible, the cytomorphologic characteristics and diagnostically essential cytochemical elements of the cell. (Yoshida, 2004)
Deactivate autolytic enzymes
Replace cellular water
Facilitate diffusion of dyes across cell boundaries
Help cells adhere to a glass slide surface.
Stop cellular and microbial growth (anti-microbial). (Bibbo, 2008)
Whilst avoiding;
Excessively shrinking or swelling cells.
Distortion or dissolving of cellular components. (Manual for Cytology, 2005)
Common fixatives used in cytology include; alcoholic based fixatives such as 95% ethanol, coating fixatives such as Polyethylene glycol, special fixatives such as Carnoy’s fixative and finally formalin based fixatives such as alcoholic formalin and formalin vapour.
Formalin (4% formaldehyde) fixes tissue by cross-linking the proteins, primarily the residues of the basic amino acid lysine. Though it is widely used in histology as the optimally preferred fixative, its uses is somehow limited in cytology. This paper is to review some of merits and demerits of the its use in cytology how it has become unpopular.
MERITS
In a study conducted by Shivakumarswamy et al., 2012, the diagnostic utility of cell block preparation using 10% alcohol-formalin as a fixative was compared with the conventional smear. In this study it was concluded that the 10% alcoholic fixative is optimal for the cell block technique, in that, they got better cellularity as formalin minimized the cell loss by forming protein cross links and gel formation that could not be dissolved by various chemicals used for processing. And this contributed to the diagnosis of malignancies by the Cell Block methods, which were reported as negative in
References: 1. Manual for Cytology, Directorate General of Health Services, Ministry of Health and Family Welfare, Government of India, November 2005. 2. Yoshida T., Fukuda T., Sano T., et al: Usefulness of liquid-based cytology specimens for the immunocytochemical study of p16 expression and human papillomavirus testing: a comparative study using simultaneously sampled histology material. Cancer (Cancer Cytopathol), 2004; 102:100-108. 3. Marluce Bibbo, MD, ScD, FIAC and David Wilbur, MD: Comprehensive Cytopathology, 2008 4. Shivakumarswamy, U., et al. (2012). "Diagnostic utility of the cell block method versus the conventional smear study in pleural fluid cytology." J Cytol 29(1): 11-15. 5. Ikeda, K., et al. (2011). "Comparison of immunocytochemical sensitivity between formalin-fixed and alcohol-fixed specimens reveals the diagnostic value of alcohol-fixed cytocentrifuged preparations in malignant effusion cytology." Am J Clin Pathol 136(6): 934-942 6. Gottschall, E. B., et al. (2005). "Effect of cytological fixative and environmental conditions on nuclear morphometric characteristics of squamous epithelial cells in sputum." Cytometry B Clin Cytom 67(1): 19-26 7. Mayall, F. and A. Darlington (2010). "The Poor Man 's Cell Block." J Clin Pathol 63(9): 837-838. 8. Dotti, I., et al. (2010). "Effects of formalin, methacarn, and fineFIX fixatives on RNA preservation." Diagn Mol Pathol 19(2): 112-122. 9. Formaldehyde Policy, Virginia Commonwealth University Office of Health & Safety Chemical/Biological Safety Section, http://www.vcu.edu/oehs/chemical/formaldehyde.pdf