Discussion :
Intrathoracic Goiter =extension of cervical thyroid tissue / ectopic thyroid tissue (rare) into mediastinum

Incidence:
5% of resected mediastinal masses; most common cause of mediastinal masses

Location:
usually anterior, 25% posterior exclusively on right side
-mostly asymptomatic
-symptoms of tracheal + esophageal + recurrent laryngeal nerve compression
-continuity with cervical thyroid / lack of continuity (with narrow fibrous / vascular pedicle)
-mass of high HU + well-defined borders
-frequent focal calcifications
-inhomogeneous texture with low-density areas (= degenerative cystic areas)
-marked + prolonged enhancement