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Folia Morphol (Warsz). 2018 Oct 29. doi: 10.5603/FM.a2018.0099. [Epub ahead of print]

The effect of prolonged formalin fixation on the staining characteristics of archival human brain tissue.

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Medical Laboratory Technology Department, Faculty of Applied Medical Sciences , King Abdul Aziz University, P.O Box 80200 Jeddah, 21589 Jeddah, Saudi Arabia; Neuroscience Research Unit, Faculty of Medicine, King Abdul Aziz University, Jeddah, Saudi Arabia.



Neurodegenerative disorders include wide range of conditions, which affect millions of people worldwide. Unfortunately, they are incurable and irreversibly progressive. Immunohistochemical staining of paraffin fixed tissues for both diagnostic and research purposes are widely used. However, large amount of brain tissues are fixed but little is known about whether they are suitable for retrospective studies. The study aimed at investigating the effects of prolonged formalin fixation time on IHC expression of some common neurodegenerative markers in archival brain specimens.


Twenty brain specimens were obtained from human cadavers in the Anatomy Department of King Abdul-Aziz University that were prefixed in 10% formalin. They were divided into two equal groups according to time of fixation, Group: 1 less than one year, Group 2: Up to 20 years. Histological examination of white and gray matter was done using H & E, Luxol fast blue (LFB) for myelin staining, Congo red for amyloid plaques, CD 68 for microglial cells, Tenascin-C (large extracellual matrix glyco protein) and Caspase 3 antibody for apoptotic cells.


For both groups, corpus callosum sections displayed myelination with LFB staining. The distribution of CD 68 positive microglial cells was evident in frontal, temporal grey matter not in corpus callosum sections. Strongly positive masses were seen in Congo red stained frontal and temporal sections. Anti-Caspase 3 immunostaining revealed positively stained neurons.


Histological and immunohistochemical techniques yielded reproducible staining results when applied to human brain tissue stored in formalin for long periods so they can be used in well preserved biobank material which are the most targeting research areas in neuropathology.


formalin fixed; human brain; immunohistochemistry; neurodegenerative markers

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