The relationship between the latent period and animal age in the development of foreign body sarcomas.

Either porous polyester-polyurethane cylindrical sponges with a diameter of 12 mm (thickness 6 mm) or rectangular sponges (dimensions 120 times 20 times 5 mm) were implanted paravertebrally in the subcutis of a total of 118 rats of different ages (1-15 1/2 months). It was established that the rate of tumor formation increased with the size of the implant from 12.1% (cylindrical sponges) to 26.6% (rectangular sponges). Furthermore is could be shown that in animal experiments it is the age of the rats that plays the decisive role in sarcogenesis and not the latend period (time from the implantation until development of the tumor), in that young animals first develop malignant mesenchymal tumors after a mean 17.2 months whereas in old rats these had already developed after 6.3 months.