Gout (Tophus)
With recurrent attacks of acute gouty arthritis, a chronic lesion called a tophus forms. The lighter areas in the photos, some round to oval, represent proteinaceous matrix left in place when dense deposits of urate crystals were removed during tissue processing. At higher magnification, note the surrounding dense collagen fibers, fibroblasts, and a giant cell. Earlier, there would have been granulation tissue with macrophages, vascular proliferation, and fibroblasts. In many cases of advanced gout, tophi are not limited to joints.