Fixation and fixatives in histopathology: a review

Abstract

If fixation is not adequate, the other processes that follow such as dehydration, clearing, infiltration, embedding, microtomy and staining, will also be inadequate. A poorly processed tissue will make it difficult for the Pathologist/Histoscientist to render a proper diagnosis. This article is aimed at elucidating more on fixatives and fixation process in histopathology. The information presented in this review was gathered primarily from an extensive literature search on PubMed, Scopus and Textbooks. Fixatives in histopathology can be grouped into simple and compound fixatives. Simple fixative is a solution or gas which contains only one active ingredient or that has a singlechemical solution. Examples include; Formaldehyde, Glutaraldehyde, Mercuric Chloride, Potassium Dichromate, Picric Acid, Osmium Tetroxide, Acetic Acid, Ethanol, Acetone and Chromic Acid. When two or more simple fixatives are combined in a solution, the resulting solution is called a compound fixative. This can be further divided into Microanatomical and cytological fixatives. Examples of a micro-anatomical fixatives include; 10% formal-saline, Heidenhain’s Susa, Boiun’s fluid, Formol Sublimate. Cytological fixatives are grouped into cytoplasmic and nuclear fixatives. Fixation terminates any ongoing biochemical reactions, and also increases the mechanical strength or stability of the treated tissues. To accomplish this, tissue samples are usually immersed immediately in a fixative fluid. The fixatives employed prevent autolysis and putrefaction from taking place. Fixatives are integral substances used in histopathology to forestall the actions of autolysis and putrefaction in tissue samples.