A 72-year-old man underwent a chest and abdominal CT examination for follow up after surgical resection of testicular cancer. He presented with oedema of the lower extremities and anaemia. The patient had normal ECG and no chest pain.

The pre-contrast thoracic scan demonstrated a 79 x 85 mm rounded mass with regular contours and peripheral calcifications, occupying the anterior and middle mediastinum, next to the right chambers.
Post contrast images (Fig. 1, 2) showed a huge thrombosed aneurysm starting at the origin of the right coronary artery, extending up to the crux. No other significant findings were present, apart from diffused tissues oedema of the extremities, abdominal and pleural effusion.
After this examination, the patient was treated with an arterial by-pass.

Aneurysms and ectasiae are dilatations of the arteries where the diameter of the vessels is more than 1.5 fold. The aneurysms are wider, ectasias are usually diffuse, involve more than 50% of the length of the artery [1, 2].
Aneurysms can be ‘true’ or ‘false’ according to the vessel layers. Dilatation may be either saccular or fusiform based on the morphologic appearance. Despite this, there are no precise criteria of the classification based on the size. Usually if the diameter of the coronary artery exceeds 20 mm (in children 8 mm), it is called giant aneurysm [2].
The prevalence of the coronary aneurysms is 0.3-5.3%. The incidence in men is 2.2% while in women it is just 0.5%. The occurrence of giant aneurysms is extremely low, 0.03% among the general population - excluding patients with congenital coronary fistula [1, 2]. RCA is most commonly affected (80-87%) followed by CX and finally LAD [1].
The main reason of the pathogenesis of aneurysms is the abnormality of the tunica media in the arterial wall. This is most commonly due to atherosclerosis (50%), congenital diseases (17%) and infectious causes (10%). This rate is different in Japan where the most dominant cause is the Kawasaki disease [2]. Venous by-pass surgery is another important risk factor as widely reported in literature [3, 4, 5].
Most of the cases are incidental findings without any symptoms. In symptomatic cases patients have complaints depending on the underlying causes. Chest pain, myocardial ischaemia or rupture, haemopericardium, cardiac tamponade or thrombosis can be detected.
The use of ECG-gated coronary angio-CT provides the possibility to diagnose. The anatomy of the coronary artery, the morphology of the aneurysm and of the arterial wall, and the presence of thrombi or plaques can be accurately evaluated. The conventional coronary angiography provides no information of the structure of the arterial wall, dilated segments may be underestimated and in case that the aneurysm is thrombosed, it may not even be seen [2]. MR imaging may show the presence of myocardiac ischaemia caused by occlusion of the distal part of the artery by thrombi.
The treatment is based on the presence of coexisting coronary disease. Conservative therapy includes anticoagulant therapy and follow-up. In case of severe atherosclerosis or to prevent severe complications percutaneous stent insertion or CABG can be performed. In Kawasaki disease the treatment is the use of high dose intravenous γ-globulin and aspirin. [2]