the diagnosis of posterior mediastinal extension of thymus was made by magnetic resonance imaging , which showed ( a ) continuity of the normally placed thymus with a posterior mediastinal mass , ( b ) identical signal characteristics between the anterior and posterior components , ( c ) homogeneous signal intensity greater than muscle and less than fat on t1- and moderately t2-weighted images which is characteristic of thymic tissue , and ( d ) characteristic posterior extension of the thymus between the superior vena cava and trachea .
C1515430
thymic tissue
C0040113
thymus