Musculoskeletal and Skin Pathology for Medical II Students

Lab 1c Tophus of Gout (03000-55070)

The tophus is the pathognomonic soft tissue lesion of gout, and consists of masses of urate crystals surrounded by an inflammatory reaction. The inflammation often contains foreign body giant cells at the edge of a collection of urates. Urate crystals are water soluble and will be dissolved out in standard histologic processing, leaving only needle-shaped empty spaces where the urates had been present. When they are preserved by special processing (alcohol fixation), they are doubly refractile under polarized light.

Slides 11 & 12 | Slide 13

Slide 13 A higher power view. The material in the center of the lesion has a crystalline appearance and is the site of the urate crystals which have been dissolved out by formalin fixation. No polarizable material is left in this specimen, but the crystalline masses and the foreign body reaction are histopathologic indicators of the diagnosis.

Digital Legends for Labs/Cases
Lab 1
1a | 1b | 1c | 1d | 1e | 1f | 1g
Gross & Radiographs
a | b | c | d | e | f | g | h 
Lab 2
2a | 2b | 2c | 2d | 2e | 2f

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Medical II

Updated August 28, 2007