Fig. 1

Local diagnosis of ectopic parathyroid cyst inside the thymus in ultrasound examination. (A) ^99mTc-methoxy-isobutyl-isonitrile scintigraphy (99mTc-MIBI) (B), enhanced computed tomography (CT) (C) and magnetic resonance imaging (MRI) (D). 99mTc-MIBI confirmed a localized and slightly hyperfunctioning parathyroid tissue in the anterior mediastinum only in an early phase, but not in a delay phase (red circle). Enhanced CT showed a cyst-like tumor in the upper anterior mediastinum (white arrow). The diameter was as large as 50 mm. MRI showed high signal on T1-weighted images due to fluid cyst contents (white arrow head) as observed in 99mTc-MIBI