Morphology of the neoplasms of the thyroid gland in Fischer 344 rats treated with 4,4'-methylene-bis-(N,N-dimethyl)-benzenamine.

Follicular neoplasms of the thyroid gland developed in 79 of 200 Fischer 344 rats of both sexes, fed either 0.0375% or 0.075% 4,4'-methylene-bis-(N,N-dimethyl)-benzenamine (MDBA) mixed with the diet. Hyperplastic changes in the follicular epithelium occurred in 12 rats fed the higher concentration of this chemical. One of 40 control rats had a follicular carcinoma of the thyroid gland.