Title: Histology: Urate Crystals in Tissue: A Novel Staining Method for Formalin-Fixed, Paraffin-Embedded Sections
Abstract: The histologic appearance of gouty tophi is usually diagnostic; however, some cases require special techniques to demonstrate urate crystals for a definitive diagnosis. A simple and specific staining method is described to demonstrate urate crystals in tissue sections. The staining principle visualizes tissue architecture with eosin in absolute alcohol without aqueous reagents to prevent loss of urate crystals. Sections stained with this method showed gouty tophi with characteristic needleshaped yellow-brown urate crystals using light microscopy and diagnostic negative birefringence with polarizing microscopy. This method preserved urate crystals in tissue sections, allowing confirmation by polarizing microscopy. If the tissue is fixed in formalin for less than 12 hours, there is no significant loss of urate crystals; however, fixation for more than 48 hours dissolves the urate crysta