“…Glazer et al (1982) reported five characteristic CT features of mediastinal thyroid: (1) anatomical continuity with a cervical thyroid, (2) focal calcification, (3) relatively high CT number, (4) rise in CT number with contrast enhancement and (5) prolonged enhancement after contrast administration. On the other hand, mediastinal involvement in recurrent thyroid carcinoma is reported to have a non-specific CT appearance, such as lymphadenopathy or chest wall invasion (Pearlberg et al 1989). In contrast, normal thymus has a bilobed, arrowhead-shaped cross-section at all ages and can be detected by residual flecks of thymic parenchyma within the gradually increasing amount of parenchymal fat (Moore etal.…”