The Right Hand Must Know What the Left Hand is Doing: A False-Positive Hotspot on the Sestamibi Scan

Imaging studies in the setting of primary hyperparathyroidism are performed to rule out an ectopic parathyroid adenoma. Although rare, false-positive scans can cause confusion and possibly more extensive procedures.

A 68-year-old woman with parathyroid hormone-dependent hypercalcemia was found to have uptake in the left midclavicular area on the parathyroid scan with sestamibi. Retention of the isotope was considered a possibility, and the sestamibi scan was repeated after injecting the isotope in the right hand and this did not show uptake in the left midclavicular area.

Sestamibi is taken up by the mitochondrial-rich adenoma cells and can help identify an ectopic location of the adenoma. Sestamibi scans are commonly performed before neck exploration to rule out an ectopic adenoma and to localize the parathyroid adenoma. Thyroid adenoma and thyroid cancer can also cause retention of isotopes. Retention of the isotope in the vein can also give an illusion of an ectopic parathyroid adenoma. Injecting the isotope in the contralateral hand can overcome this retention issue.

Uptake on parathyroid scan outside of normal embryologic decent of the parathyroid gland should raise the possibility of a false-positive uptake.