Alterations of liver and spleen among workers exposed to vinyl chloride

Preliminary review of hepatic biopsy and autopsy specimens obtained from workers engaged for prolonged periods in the polymerization of vinyl chloride indicates a fibrotic precursor lesion in the liver. It is the only lesion in some instances but also was found in the uninvolved liver of patients with angiosarcoma and in two instances in liver biopsy specimens obtained before angiosarcoma developed. This precursor stage is characterized by a conspicuous subcapsular fibrosis, a nonpathognomonic progressive portal fibrosis, and a borderline increase of intralobular connective tissue, all associated with focal stimulation of sinusoidal lining cells and hepatocytes. This precursor stage is often accompanied by splenomegaly with enlarged Malpighian follicles and in some instances by portal hypertension requiring portacaval shunt because of variceal hemorrhage. The portal hypertension is explained by increased splenic blood flow in the face of nondistensible fibrotic portal tracts as well as Glisson's capsule. Transition to angiosarcoma is preceded by focal dilatation of sinusoids with even greater activation but dedifferentiation of their lining cells. This lesion is presumably the result of stimulation of various hepatic as well as splenic cells by vinyl chloride or its metabolites. The demonstrated evolution is identical with that following prolonged exposure to inorganic arsenicals. It is postulated also that other instances of inconspicuous hepatic fibrosis associated with splenomegaly and often with portal hypertension, a combination designated as Banti's syndrome or "idiopathic portal hypertension," are the result of a toxic, possibly environmental agent, particularly since the disease is found with greater frequency in some parts of the world. The delineation of the fibrotic precursor stage in the liver may assist in the epidemiologic studies of the vinyl chloride-induced injury.