Carcinogenic effect of di-isopropanolnitrosamine on the rat thyroid gland.

Up to a 50% rate of thyroid gland tumours was induced in Sprague-Dawley rats after s.c. administration of di-isopropanolnitrosamine (DIPN). The neoplasms occurred both unilaterally and bilaterally, and were identified histologically as adenomas and adenocarcinomas of follicular epithelium origin. In a few instances, adenomas were observed as early as 18 weeks after commencement of treatment. Most adenocarcinomas could be observed macroscopically, and frequently demonstrated infiltration into the surrounding muscles.