Invasive character of malignant endothelial cells in vinyl-chloride-induced liver angiosarcoma

Two cases of vinyl-chloride-induced angiosarcoma of the liver were investigated with special reference to the invasive character of malignant endothelial cells. Histological findings of the liver were similar in both cases. The liver angiosarcoma was multicentric and consisted of three portions: a peripheral parenchymal area, an intermediate mottled area, and a central cavernous area. Microscopically the intermediate area showed a mixture of fibrosis and cell infiltration of various patterns. At the periphery, yellowish brown parenchymal tissues remained and were always associated with sinusoidal changes, from non-cellular dilatation to trabecular growth of the small round cells. Under electron microscope, the small round cells showed direct contact with red blood cells and hepatocytes. Thus, the sinusoidal small cell infiltration is thought to be an initial lesion of angiosarcomatous transformation. Because none of the liver is free from these sinusoidal changes, partial hepatectomy would not be indicated even in a patient with few cavernous lesions.