Tc-99m sestamibi localization of an ectopic mediastinal parathyroid tumor in a patient with primary hyperparathyroidism.

A 50-year-old woman presented with pain and tenderness in the right flank. Urogram and ultrasound demonstrated the presence of an 8-mm calculus in the right kidney. There were persistently elevated serum calcium levels ranging from 10.7-11.4 mg/dL (normal range: 8.5-10.5) and borderline low serum phosphate levels of 2.4-2.9 mg/dL (normal range 2.5-4.5). Serum albumin levels were normal. The patient's parathormone levels were elevated and a diagnosis of primary hyperparathyroidism was made. An MRI of the neck failed to reveal evidence of parathyroid pathology. Tc-99m sestamibi imaging demonstrated no abnormal parathyroid tissue in the neck, but clearly showed an abnormal focus in the anterior mediastinum.