An unusual finding of giant fat-rich retroperitoneal masses in a patient with Graves' disease.

We report the case of a 48-year-old man who was unexpectedly found by abdominal ultrasonography to have large retroperitoneal masses accompanied by Graves' disease. Computed tomography and magnetic resonance imaging further demonstrated giant fat-rich soft masses arising within both renal sinuses. Histopathological examination of the mass was performed twice at 5-year intervals, with both examinations indicating fatty tissue cells with chronic fibrous panniculitis. Intravenous pulse therapy and successive oral glucocorticoid therapy were ineffective against Graves' ophthalmopathy or mass lesion. An antithyroid hormone regimen was followed by subtotal thyroid resection, leading to improvements in hyperthyroidism. Mass growth then attenuated slowly as the thyroid hormones returned to normal levels. The long-term follow-up of this patient should carefully monitor the appearance of warning signs such as mass effects.