[Brown tumor of the sternum--a potential cause of false-positive result on parathyroid scintigraphy with Tc-99m sestamibi].

Parathyroid scintigraphies have been used to detect pathological parathyroid glands either before as well as after the parathyroid resection surgery in patients with hyperparathyroidism. Although this test presents high specificity for detection of increased parathyroid glands, there exist causes of false positive results. In the present article, we report a case of a renal transplanted patient, with multiple lytic lesions on pelvic bones reported as brown tumors, who presented a focal uptake in the anterior portion of the superior mediastinum on Tc-99m sestamibi scintigraphy. This focal uptake, initially thought to be an ectopic parathyroid gland, after a more detailed analysis and the performance of other imaging diagnostic tests was demonstrated to be a brown tumor of the sternum.