Early onset of spontaneous renal preneoplastic and neoplastic lesions in young conventional rats in toxicity studies.

Although occurring in aged laboratory rodents, spontaneous renal tumour are unknown in animals younger than 18 weeks. A survey on renal preneoplastic and neoplastic lesions has been performed on Sprague-Dawley rats from general toxicology studies over the period January 2004 - May 2006. Data from 2249 rats necropsied and 1206 rats (688 males and 518 females) examined microscopically from 52 studies, are reported.