Osteosarcoma associated with Thorotrast administration: report of two cases and literature review.

Two cases of osteosarcoma are described arising in patients who had undergone angiography with Thorotrast during childhood. In both patients, there was radiographic and pathologic evidence of radioactive thorium dioxide deposition in bone as well as throughout the reticuloendothelial system. Thorotrast deposits were demonstrated in the immediate vicinity of the primary tumors by both histology and autoradiography. Previous cases of osteosarcoma associated with Thorotrast administration from the literature are cited, and possible causal relationships are discussed between thorium retention in bone and neoplastic transformation by chronic radiation.