Ultrastructure of a sclerosing hemangioma of the lung

A typical sclerosing hemangioma of the lung was examined with the electron microscope. The ultrastructural features of the predominant cells are considered to be those of endothelial cells. The participation of these cells in the formation of primitive vascular spaces supports the concept that the lesion is primarily vascular proliferative or endothelial rather than of pulmonary epithelial origin. A secondary role is ascribed to the various cellular elements accompanying a process of aging and vascular senescence culminating in fibrous obliteration and xanthomatous transformation.