Spontaneous Renal Cell Tumors in Long‐Evans Cinnamon Rats

Neoplastic lesions of the kidneys in untreated Long-Evans Cinnamon (LEC) rats of 57–118 weeks old (85 males and 34 females) and male F344 rats of 64–93 weeks old (59 males) were examined histologically. The incidences of renal cell tumors in male and female LEC rats were 6/80 (8%) in weeks 57–65, 3/19 (16%) in weeks 66–75, 3/8 (38%) in weeks 76–105 and 7/12 (58%) in weeks 106–118. Of these tumors, 13 were microscopic adenomas and 7 were renal cell carcinomas. The copper content of the kidneys was about three times higher in LEC rats than in F344 rats (P<0.001), but the iron content of the kidneys was similar in the two strains.