Figure 17. Ectopic focal localization and an abnormal thyroid. The patient underwent surgical exploration of the neck with right hemithyroidectomy; results of the surgical exploration were negative. Early Tc-99m MIBI image shows an ectopic parathyroid adenoma in the left side of the chest (arrow). The residual left thyroid lobe is seen (arrowheads). The diagnosis was an ectopic parathyroid adenoma of the mediastinum. Pearl: Parathyroid adenomas may be overlooked at initial or repeat surgery because they occur in a distant location. Pitfall: Imaging with a field of view limited to the neck will cause ectopic sites to be overlooked, as in this case. Imaging should extend from the base of the jaw to the base of the heart.