HLAB 2341 Registry Review - Fixation

The choice of fixative is the most important decision in the histopathology lab because it determines the preservation and stability of tissue samples. Fixatives are used to prevent tissue degradation, maintain cellular structure, and prevent the growth of microorganisms. The choice of fixative can impact the quality of the samples, the ability to perform accurate diagnoses, and the overall success of the histopathology testing process.

ALL non additives will be coagulants as welll. Mercury, zinc, and picric acid are additive fixative, but will be coagulants as well.

Methanol is an alcohol and all alcohols are non-additive fixatives. Non-additive fixatives pull out water, or dehydrates the tissue, but does not bind to the tissue, which then fixes the tissue by making it more stiff.

Fixation serves several purposes in laboratory techniques such as histology. It helps minimize processing distortions, preventing any changes or artifacts that may occur during the subsequent steps. It also prevents putrefaction, which is the decay or destruction of cellular proteins by bacteria. Additionally, fixation prevents autolysis, the enzymatic destruction of cells that can occur after death. Another purpose is to stabilize proteins, preserving their structure and preventing degradation. Lastly, fixation enhances staining when using a mordant like Bouin or Zenker, improving the visibility and contrast of the tissue samples.

Ethanol, Glutaraldehyde, Formaldehyde are all fixatives commonly used in tissue processing. These fixatives do not form a solid gel and do not require a vacuum for liquid reagents to penetrate the tissue.