The diagnosis of acute type-A aortic dissection is predominantly based on the demonstration of an intimal tear or a dissection membrane. We describe another pathogenetic mechanism in a patient with the typical features of acute aortic dissection with pericardial tamponade, and a giant aneurysm of the ascending aorta. However, no dissection membrane, rupture site, or intimal tear could be demonstrated by transesophageal echocardiography, intraoperatively, or histologically. The histological work-up showed an extreme form of cystic medial necrosis with intramural hemorrhages consistent with a leaking aneurysm. Hence, in a patient with a symptomatic aneurysm of the aortic root and pericardial tamponade, obvious intimal dissection or rupture does not always have to be present echocardiographically or intraoperatively. A different presentation can occur in the setting of an extreme medial necrosis, where blood leaks through the aortic wall causing intramural hemorrhages with intimal leaks invisible to the surgeon's or echocardiographer's eye. This process is clinically indistinguishable from type-A aortic dissection.