[Effect of gonadectomy on the carcinogenesis induced by a foreign body implant]

The incidence of tumors arising near a plate in male rats castrated before and after its being implanted into the loose connective tissue was studied. Tumors occurred in 26 animals out of 49 in control (group 3) (53.2%); in 16 out of 28 rats castrated one month after implantation (group 2) (57.1%), and in 5 out of 21 rats castrated one month before implantation (group 3) (23.8%). Connective-tissue capsules in group 3 were thin 12 months after implantation and were absent in several animals thus suggesting resorption. However, collagen capsules formed around the plates in groups 1 and 2 had become much thicker by the same time. Tumor growth was inhibited in gonadoectomized animals which formed collagen capsules after plate implantation. In view of the available data on reduced synthesis of collagen in young castrated male rats, the rapid resorption of collagen capsules in group 3 seems to have been due to their thinness. Therefore, inhibition of tumor growth around the plates was in correlation with fast resorption of collagen capsules. It is suggested that collagen resorption inhibition is a factor contributing to tumorigenesis.