Foreign-body tumorigenesis: number, distribution, and cell density of preneoplastic clones.

Double 15 times 22-mm plastic films (two films on top of each other) were implanted subcutaneously in CBA/H-T6 mice. After 7.5, 8.5, and 9.5 months the films were removed. Each interior film (next to the abdominal wall), covered by a cell monolayer on one side only, was cut in four 7 times 10-mm segments. Wiping to 5 times 7, 4 times 4, 3 times 3, or 2 times 2 mm reduced the cell areas on three of them. They were then transferred to (CBA/H times CBA/Br)F1 or (CBA/H-Ty times CBA/Br)F1 recipient mice. Tumors arising from transferred film segments were analyzed as to chromosome number and morphology, sarcoma type, degree of anaplasticity, and posttransfer latency. We used these criteria to determine whether tumors originated from the same or different clones. From this information it was estimated that preneoplastic clones were present in limited numbers and that they were either widely disseminated or spatially restricted on the implant surfaces. The extent of clone dissemination appeared to be related to preneoplastic progression.