EComment. Aneurysm of the internal mammary artery may imitate a mediastinal mass

Abstract

We read with great interest the presentation by Lindblom et al. [1] regarding an aneurysm of the left internal mammary artery (IMA), which is a rare and potentially devastating pathology. The case presented has diagnostic challenges and a spontaneous rupture resulting in life-threatening bleeding. The authors suggested the importance of the careful interpretation of radiological findings and the significance of multidisciplinary collaboration between radiologist and clinician. We fully agree with their implications regarding this unusual scenario and would also like to add a short comment on this topic. Mediastinal masses may present a challenge in diagnosis. A mediastinal mass is sometimes detected during routine screens by chest radiography. Mediastinal masses generally originate from the thymus, thyroid, parathyroid, and lymph glands. Vascular pathologies are among the most important causes for mediastinal masses and should always be excluded [2-4]. Vascular lesions include aneurysms of the thoracic aorta, the brachiocephalic artery, the IMA, the intercostal artery, the innominate vein, the superior vena cava, the azygos vein, and the internal mammary vein [2]. True IMA aneurysms are uncommon clinical entities. They are associated with atherosclerotic disease, hereditary connective tissue disorder, fibromuscular dysplasia, type 1 neurofibrinomatosis, vasculitis, and idiopathic causes. Whildhirt and associates[2] reported a case with an atherosclerotic aneurysm of the right IMA, which is a rare cause of a mediastinal mass. Iatrogenic pseudoaneurysms after sternotomy arise from a variety of vessels including the coronary artery, saphenous vein graft(SVG), the intercostal arteries and the IMA. Pseudoaneurysm of the IMA after sternotomy is extremely rare. It may result from central venous catheterization, pacemaker lead implantation, local infection, and trauma to the branches of IMA by steel wires, or may be spontaneous. Iatrogenic IMA pseudoaneurysm may present as an asymptomatic mediastinal mass. However, a high index of suspicion is important in the diagnosis of pseudoaneurysms of the IMA, especially in a haemodynamically unstable patient after sternotomy [3]. Almassi [4] presented a case of an aneurysm of the internal mammary vein presenting as an enlarging anterior mediastinal mass. Diagnosis of internal mammary vein aneurysm can be established by contrast computed tomography scan of the chest with image acquisition in the venous phase. This vascular pathology should be considered in the differential diagnosis of mediastinal masses[4]. Aneurysm of saphenous vein graft(SVG) may also present as a mediastinal mass and is a rare but potentially fatal complication of coronary artery bypass grafting(CABG). Many factors may actually play a role in the development of SVG aneurysm. This aneurysm may be located anywhere along the graft[5]. A computed tomographic scan with intravenous contrast, magnetic resonance imaging and echocardiography is helpful in identifying the consistency, vascularity, and patency of the SVG aneurysm [5]. Coronary angiography also demonstrates the vascular nature of this lesion and can detect other lesions in the native coronary artery. In a patient who has undergone CABG, the appearance of a mediastinal mass on a chest radiography should raise the suspicion of an SVG aneurysm [5]. We think that patients presenting with a mediastinal mass should always be evaluated first for the existence of these vascular abnormalities. Conflict of interest: none declared