Synchronous Ectopic Thyroid Gland and Ectopic Parathyroid Adenoma on ^99mTc-Sestamibi Scintigraphy and Correlative Imaging

(A) ^99mTc-sestamibi SPECT image at 15 min (left) shows uptake at posterior tongue (thick arrow) and mediastinal focus (horizontal thin arrow). SPECT image at 2 h (right) shows posterior tongue tracer washout (thick arrow) suggesting ectopic lingual thyroid, with persistent uptake in mediastinal focus (horizontal thin arrow) consistent with ectopic parathyroid adenoma. Physiologic uptake is seen in salivary glands (oblique arrows). Uptake at anterior tongue region (arrowhead) is likely salivary activity. (B) ^99mTc-sestamibi SPECT at 2 h (left) shows focal uptake in anterior superior mediastinum (arrow), with axial CT component of SPECT/CT (right) showing correlating 1.6-cm lesion (arrow) consistent with ectopic parathyroid adenoma. Other peripheral uptake is artifactual activity in muscles. (C) Axial 4-dimensional parathyroid CT scan shows 39 Hounsfield units (HU) within lesion on precontrast phase (left), 161 HU hyperenhancement on arterial phase (middle), and 89 HU washout on delayed phase (right), rendering high confidence for parathyroid adenoma.