Fig. 23.21 
Cushing's syndrome: malignant thymic ACTH-secreting carcinoid tumour demonstrated by CT. 
Ectopic ACTH can be produced by carcinoid tumours of the thymus. These enhanced CT scans show in the right picture a 4cm ACTH-producing tumour lying just in front of the ascending aorta. The tumour has enhanced slightly with contrast medium but not as markedly as the vascular structures. The left scan shows enlarged anterior mediastinal lymph nodes at a higher level.