Intracisternal type A particles occurring in foreign body-induced sarcomas.

Eight sarcomas induced in mouse strains CBA/H, CBA/HT6, and C57BL/10ScSn (or their hybrids) by s.c. implantation of smooth or roughened plastic films or glass pieces were examined electron microscopically. Type A virus particles were detected within dilated ergastoplasmic cisternae of the sarcoma cells from five mice. The doughnut-shaped particles measured 90 to 100 nm and were seen to bud from membranes of the granular endoplasmic reticulum. All five virus-positive sarcomas developed in secondary hosts that had received segments of cell-laden implants and/or surrounding tissue capsules transferred from the original implant carriers during the period of nonneoplastic foreign body reaction. In all cases the tumors were derived from cells of the original host. No virus particles were found in three sarcomas that had developed directly in original implant carriers.