Mast cells in human aorta.

Aortic specimens from 111 autopsy and 23 surgical cases were examined by light and electron microscopy. Differential mast cell counts were made of three aortic segments (ascending, thoracic, and abdominal) and layers (intimal, medial, adventitial). The mast cell counts varied considerably from case to case and sector to sector and generally showed no correlation with age, sex, or atherosclerotic severity. However, intimal mast cells were fewer in number in areas of lipid accumulation than in areas of diffuse intimal thickening without lipid accumulation. The reduction in the number of intimal mast cells may play a part in the localization of atherosclerosis.