Hepatic tumors of rabbits induced by cycad extract.

Fifteen rabbits were administered cycad extract by gastric intubation, 1 ml/rabbit, once a week for 27 or 33 weeks. The extract contained 16.6 mg of cycasin/ml. Out of 9 rabbits surviving over 200 days, 7 animals had malignant neoplasms developing in the liver. Histological and electron microscopic examinations of the developed tumors revealed that they were malignant hemangioendotheliomas. The animals showed no proliferation of hepatic cells or any tumor development in other organs.