Internal mammary artery atherosclerosis: an ultrastructural study of two cases.

Atherosclerosis of the internal mammary artery (IMA) is generally regarded as a rare (but existent) pathological entity with only a few cases reported in the most recent literature. The only study which to our knowledge has investigated the ultrastructural features of IMA atherosclerosis, demonstrate the presence of endothelial cells loss, defects of internal elastic lamina with no evidence of lipid accumulation. In the present study, we describe two cases of IMA atherosclerosis in which ultrastructural analysis revealed the presence of a typical atherosclerotic plaque morphology with infiltration of inflammatory cells, formation of intraplaque lipid pools, and accumulation of lipid-laden foam cells throughout the thickened intima, never described in this rare lesion before. Microscopically, the lesions were also characterized by intimal thickening, invagination of endothelial cells, migration of smooth muscle cells with splitting, fenestration and/or fragmentation of the elastic sheets. Our observations add new data to the scarce and contradictory literature and to this largely understudied vascular disorder.