SPONTANEOUS RENAL TUBULAR CARCINOMA IN FISCBER-344 RAT LITTERMATES

Two of 632 Fischer-344 rats in a food restriction study had spontaneou s, bilateral, multicentric renal tubular cell carcinomas. Although the re were 104 litters represented in this study, both rats that develope d this rare neoplasm were from the same litter. The littermates, one m ale and one female, were in the food-restricted treatment groups (60% of ad libitum intake) and were 550 and 447 days old, respectively, at death. The probability that the two rare bilateral renal neoplasms occ urred by a chance event in littermates is approximately 0.8%. The appa rent familial predisposition for development of specific types of neop lasms emphasizes the importance of randomization of individuals into t reatment groups and consideration of lineage for rare tumors.