Cystic thymoma: diagnosis by cross-sectional imaging.

Thymomas are the most common primary tumours of the anterior mediastinum in adults, and are composed of a mixture of lymphocytes and epithelial cells in varying proportions, with scattered cystic regions of various size seen in 40% of thymomas pathologically (1). However, those that resulted in almost complete cystic transformation have been reported rarely (24). The present case report describes a patient with cystic thymoma that was evaluated pre-operatively by magnetic resonance imaging (MRI) and computed tomography (CT).