Absence of uniform progressive growth of long-term transplants of rat liver neoplastic nodules.

Fragments of normal rat liver and neoplastic nodules induced by feeding 0.02% N-2-fluorenylacetamide for 20 weeks were transplanted into the inguinal mammary fat pads of syngeneic rats. All animals were Charles River inbred male albino rats of the CDF strain derived from the F344 strain. Normal liver transplants and neoplastic nudule transplants were detected histologically in the transplant site up to 24 and 66 weeks of survival, respectively. Of 30 nodule transplants followed up to 121 weeks, only 1 neoplastic nodule developed progressive neoplastic growth. The tumor that arose in the transplant site from this nodule was a well-differentiated adenocarcinoma with mucin production. Thus rat liver neoplastic nodules lack the high frequency of progressive growth previously demonstrated for carcinomas.