Diisopropanolnitrosamine (DIPN) induced rat thyroid lesions. I. A histological classification.

DIPN induced localized lesions of the rat thyroid gland are described histologically and classified into three major types: type 1, foci of cellular alteration; type 2, proliferative nodules; and type 3, overt carcinomas. Follicular, papillary and mixed papillofollicular subtypes are recognized in the type 2 lesions, and follicular, papillary, anaplastic and mixed subtypes in the type 3 lesions. The nature of the individual lesions is discussed.