Tumors induced in mice by N-methyl-N-formylhydrazine of the false morel Gyromitra esculenta.

Continuous administration of 0.0078% N-methyl-N-formylhydrazine (MFH) in drinking water to 6-week-old outbred Swiss mice for life produced tumors of the liver, lung, gallbladder, and bile duct. The incidences of tumors in these four tissues were 33, 50, 9, and 7%, whereas in the untreated controls they were 1, 18, 0, and 0%, respectively. The higher dose (0.0156% MFH) given under identical conditions had no tumorigenic effect, since it proved too toxic for the animals. Histopathologically, the lesions were classified as benign hepatomas, liver cell carcinomas, adenomas and adenocarcinomas of the lungs, adenomas of the gallbladder, cholangiomas, and cholangiocarcinomas. Since the edible false morel Gyromitra esculenta contains a high amount of MFH, the human population should be dissuaded from consumption of this dangerous mushroom.