Masayasu Kojimahara

Ultrastructural study of hemangiomas. 4. Cavernous hemangioma of the liver.

Seven cases of cavernous hamangioma of the liver found accidentally at autopsy were studied by electron microscope. The structures of the hemangioma consisted of capillaries and the intervening stromal cells. The endothelial cells contained pinocytotic vesicles, scattered ribosomes, rough endoplasmic reticulum, and Golgi apparatus. A distinct basement membrane was present beneath the endothelial cells, and multilaminated arrangement of the basement membrane was sometimes observed beneath the endothelial cells. The endothelial cells also contained numerous cytoplasmic filaments, but contained sparse specific endothelial granules. The internal elastic lamina was hardly seen at all in the hemangioma. The stromal cells showed typical smooth muscle cells, modified smooth muscle cells, and fibroblast‐like cells. Elastic tissue as well as collagen fibers was present within the intervening stroma. Neither adventitia nor nerve fibers were found in the cavernous hemangioma. It is thought that cavernous hemangioma of the liver may be of a hamartomatous nature. ACTA PATHOL. JPN. 36:1477‐ 1485, 1986.,

ULTRASTRUCTURAL STUDY OF HEMANGIOMAS

A case of benign hemangioendothelioma which occurred in the hard palate was observed and its electron microscopic findings were described. The endothelial cells contained an abundance of cytoplasmic filaments, but they contained a small number of Weibel‐Palade bodies. Two types of endothelial cells, light and dark, were found in our specimen. The former had a cytoplasm with an abundance of ribosomes, rough endoplasmic reticulum and scant filaments. The latter had a cytoplasm with numerous cytoplasmic filaments and a well‐developed Golgi apparatus. Tight junctions were seen between the endothelial cells. The majority of the pericytes were accompanied with the vessels in the tumor. Three types of pericytes were recognized: endothelial cell‐like, fibroblast‐like, and smooth muscle cell‐like pericytes.

INTIMAL LAMINATED ELASTOSIS IN THE INTRARENAL ARTERIES An Electron Microscopic Study

Using kidneys from diabetic patients, the morphogenesis of elastic hyperplasia (“laminated elastosis”) in the intrarenal arteries was studied by electron microscopy. In the thickened intima, myointimal cells produced ground substance, collagen fibers and elastic tissue. The elastic tissue was stained black electron microscopically with orcein. Newly‐formed elastic tissue in the intima was first found on either the basement membrane or basement membrane‐like materials around the myointimal cells and endothelial cells. Subsequently, small areas of elastic tissue aggregated and fused to form larger areas of elastic tissue or concentric thick elastic laminae, the latter containing a large number of collagen fibrils. Upon treatment with elastase, newly‐formed elastic tissue was digested, but the microfibrillar component remained unstained.

ULTRASTRUCTURAL OBSERVATIONS ON BIFURCATIONS IN RAT CEREBRAL ARTERIES

The bifurcation pads (“valve‐like projections”) in the anterior cerebral arteries of rats with long‐term hypertension were studied electron microscopically. The rats ranging in age from 2 to 10 months were sacrificed after bilateral renal artery constriction at 5‐week‐old. In the bifurcation pads (intimal pads) of hypertensive rats, smooth muscle cell damage first appeared in the roots of the pads as well as underlying media in the form of granular, vesicular, and somewhat tubular structures (200–1500 Å in diameter). Thereafter, with a lapse in time after the operation, these abnormal substances increased around the smooth muscle cells which were arranged in the marginal zones of the pads. Deeply arranged intimal smooth muscle cells which were embedded in an abundance of ground substances were only damaged in rats with very long‐term hypertension. The medial smooth muscle cells beneath the pads manifested lesions which were more marked and diffuse than in the intima. These smooth muscle cells were bizarrely atrophied and abnormal substances which might be derived from necrotic smooth muscle cells were found around them. Basement membrane‐like substances, either thick or multilaminated, were also present around them.