Lege Artis Medicinae

[A simple method to demonstrate urate crystals in formalin fixed tissue]

BÉLY Miklós, KRUTSAY Miklós

JUNE 20, 2013

Lege Artis Medicinae - 2013;23(05-06)

[In our previous study we refuted the thesis that sodium urate crystals are not, or only rarely detectable in formalin-fixed histological samples because they dissolve in the aqueous formalin solution. Our observations indicate that dissolution of urate crystals is primarily caused by haematoxylineosin staining. Undeniably, however, urate crystals are partially dissolved in the aqueous solution of formaldehyde, and thus a small amount of urate deposits may totally dissolve from tissue samples. The aim of the present study was to identify those steps of the staining procedure that are responsible for the dissolution of urate crystals. We found that the dissolution of urate crystals during the course of staining was caused by the combined effects of haematoxylin staining, treatment with 1% aqueous lithium carbonate solution and dehydration with acetone. As the simplest histological method for the detection of urate crystals, we recommend examining unstained sections (mounted with Canada balsam) of formalin-fixed, paraffin-embedded tissue samples in polarised light. According to our previous study, about two thirds of urate crystals remain detectable on unstaied sections, whereas haematoxylin-eosin stained sections of the same tissue samples (derived from patients with gout) did not contain urate crystals. In the samples where urate crystals could be detected in haematoxylin- eosin stained sections using polarised light, the unstained sections contained much more crystals, which shows that dissolution is greatly decreased on unstained sections.]

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