various malignant tumors of the liver , especially liver angiosarcoma , have been described after occupational exposure to vinyl chloride monomer . 
 we present the case records and pathologic findings of two plastic industry workers who had been exposed to high concentrations of vinyl chloride . 
 these workers developed hepatic neoplasms , angiosarcoma , or hemangiopericytoma . 
 we discuss the histogenesis of these tumors ; the common vascular origin and the mutual transformation of these two tumors suggest that the hemangiopericytoma may also have developed during occupational exposure to high concentrations of vinyl chloride monomer.imagesfigure 1figure 2