High incidence of spontaneous transplantable tumours in BDX rats.

Untreated male and female BDX rats were observed over a period of 30 months for spontaneous tumours of a size suitable for transplantation. At the age of 13-30 months 60/97 animals developed tumours, 53 of which were considered as malignant, and 7 as benign tumours. The spectrum of malignant tumours included sarcomas of connective tissue and bone, skin carcinomas, tumours of the lung, the gastrointestinal tract, the genito-urinary tract, the mammary glands, the testis, the adrenal glands and also sarcomas of the neural system and malignancies of the lymphoreticular system. Out of 41 tumours implanted s.c., 34 of them could be passaged further. The primary latent period varied between 1 and 12 months.