Dissecting aortic aneurysms: a clinicopathological study. II. Histopathology of the aorta.

The aortas from 83 patients with dissecting aneurysm were studied histologically. There were two examples of giant-cell arteritis, one of non-specific arteritis and one of syphilis. Apart from these, no constant feature was found in the cases of dissection when compared with 20 controls. In particular there was no difference in the grades of cystic medial necrosis, medionecrosis and fibrosis. Focal fragmentation of elastica was present in the majority of dissections (63 per cent) but similar abnormalities were seen in most controls (85 per cent). The vasa vasorum showed no special features in dissection. Intimal fibrosis and intimal longitudinal muscle were present in both groups studied. Sixteen cases showed 'old' dissections as manifest by either granulation tissue or fibrosis. The histopathological features of the four cases diagnosed clinically as having Marfan's syndrome did not differ from controls.