[Study of atherosclerosis regression in the elderly--central depression and its correlation to ulcerated plaques]

Atherosclerotic plaque with central depression (depressed lesion) was firstly proposed in our previous report as one of the morphological features of regressed lesions, which was characterized by the presence of isolated, well defined lesions with a centrally depressed area and smooth surface. They were obviously different from atherosclerotic plaques with ulceration (ulcerated plaques) in elderly autopsy cases. In this study, 30 ulcerated plaques obtained from specimens of the elderly aortas were histologically and immunohistochemically investigated to clarify the morphogenesis of the depressed lesion and its correlation to the ulcerated plaque. These depressed lesions were divided into 4 groups according to their derivation; (a) fused lesion of multiple fibrous plaques, (b) regressing lesion of plaques, (c) healed ulcerated plaques, and (d) mixed type of these lesions. Regeneration of endothelial cell was noted in the peripheral zone of ulcerated plaques, and collagen type IV was also increased in the stroma of these ulcerated plaques. These were healed ulcerated plaques. The ulcerated plaques with complete restoration of endothelial cells on the ulcerated surface may become atherosclerotic plaques with central depression. These lesions are one of the histological features of regression in advanced atherosclerosis.