A case report of dystrophic localized amyloidosis that developed in the left thigh.

We report on a 50-year-old man with dystrophic localized amyloidosis who noticed a soft tumor in his left thigh about 20 years ago, after which the tumor has gradually enlarged. The multicystic tumor showed hemorrhage, hematoma, necrosis, fibrosis, and tiny nodules and various polymorphous granulomas were observed. One was rich in eosinophilic amorphous materials and cholesterol crystals, and was poor in cell reaction. Another was formed by granuloma consisting of multinucleated giant cells, foamy cells, and macrophages. Transitional granulomas between the two were also observed. The materials showed eosinophilia and red staining and apple-green birefringence in polarized light by alkaline Congo-red stain, and they were also resistant to potassium permanganate pretreatment. They were also positive for amyloid P component and consistently negative for amyloid A, κ- and λ-light chains, β2-microglobulin, and transthyretin. Therefore, it was suggested that this might be an amyloid derived from the hematoma, which has not been reported to date.