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Author: Mikael Häggström [notes 1]


A tophus specimen should be sent dry to the pathology department, and not be put in formalin.[notes 2]

Gross processing

A large tophus.

Preferably make a touch prep for polarized light microscopy. At least if urate crystals are not initially detected, take sections to be put in 100% alcohol and tell the histology lab to prepare it as per gout protocol.[notes 2] With characteristic crystals on a touch prep, sections may possibly be submitted in formalin.[notes 2]

Microscopy evaluation

On a touch prep, look for needle-shaped crystals of urate. On polarized light, these will have negative birefriengence.


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. 2.0 2.1 2.2 Formalin dissolves the crystals.

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  1. Bruce M Rothschild. Gout and Pseudogout Workup. Medscape. Updated: Jun 30, 2020