Figure 5b. Right-sided retrosternal goiter. (a) Posteroanterior chest radiograph demonstrates a thyroid goiter (arrow) extending into the middle mediastinum, obliterating the right paratracheal stripe, and causing deviation of the trachea to the left (black arrowhead). Above the level of the clavicles, the margins of the mass are not sharp (white arrowhead), indicating that the mass has an anterior mediastinal component. (b) CT scan shows the mass (arrow) between the trachea and right lung, a location that explains the obliteration of the right paratracheal stripe seen in a. There is no contact between the anterior component of the mass and the lung (arrowhead) at the level of the clavicular heads, a relationship that continues above the level of the clavicles. This finding explains why the lateral border of the anterior mediastinal component above the level of the clavicles is not sharp in a.