Both subcutaneous and hepatic
hemangiosarcomas were induced in mice exposed to
vinyl chloride monomer, and for the first time, the ultrastructure of
hemangiosarcomas related to
vinyl chloride exposure has been described. The subcutaneous
hemangiosarcoma developed in a mouse's ear 29 weeks after exposure to 10 ppm
vinyl chloride for 4 weeks, and the hepatic
hemangiosarcoma was found in a mouse's liver at necropsy 56 weeks after exposure to 600 ppm
vinyl chloride for 4 weeks. Both
tumors showed a localized, cystic nodular appearance with a dark red tone. Histologically, an angiomatous architecture, the presence of neoplastic mesenchymal cell aggregates, focal
necrosis, and hemorrhagic foci were common. Ultrastructurally, two neoplastic cell types, a mesenchymal and a well-differentiated endothelial cell type, were identified in both
tumors. In addition, in the hepatic
tumor, a pericyte-like neoplastic cell was also present. The incidence of
hemangiosarcoma was much lower than that of lung
tumors (alveologenic
tumor) in mice exposed to
vinyl chloride at the same concentrations for the same duration. This study suggests that there is no basic difference in ultrastructure between the
vinyl chloride-induced
hemangiosarcomas and
hemangiosarcomas not related to this chemical exposure.