Localized insulin-derived amyloidosis in patients with diabetes mellitus: a case report.

Three patients with insulin dependent type 1 diabetes mellitus and one with insulin dependent type 2 diabetes mellitus developed localized amyloid tumors at their general insulin injection sites. All 4 patients (two women and two men) were treated with modern recombinant human insulin or insulin analogues. In addition, 1 patient had used both recombinant and animal insulin. The amyloid tumors were resected and examined histologically using Congo red staining and immunohistochemistry. Insulin was found to be the major component of the amyloid tumors in all four patients. These 4 cases were diagnosed recently within a relatively short period of time, which leads to the conjecture that local insulin-derived amyloid tumors remain principally a differential diagnosis of skin tumors in insulin-dependent diabetic patients.