Tc-99m uptake in a parathyroid adenoma. Potential pitfall in Tc-99m/Tl-201 subtraction imaging.

The authors describe a patient with primary hyperparathyroidism who had a large mediastinal parathyroid adenoma that avidly concentrated both Tc-99m pertechnetate and Tl-201. This unusual finding is presented as another potential reason for false-negative findings in Tc-99m/Tl-201 subtraction scintigraphy in hyperparathyroidism.