CT and MRI findings of carcinoma showing thymus-like differentiation.

Carcinoma showing thymus-like differentiation (CASTLE) is a rare tumor that occurs in the soft tissue of the neck or in the thyroid gland. We report a case of CASTLE in a 54-year-old man presenting with hoarseness. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a mass enclosing the right carotid artery with the shape of lobulation and invasion to the trachea. The mass was hypointense on T1-weighted imaging and, on T2-weighted imaging, showed a hyperintense periphery with isointense center relative to muscle. In dynamic MRI, the mass revealed gradual but slight heterogeneous enhancement from the periphery. Diagnosis was confirmed by histopathology.