ABSTRACT
Among the many cancers that were found, the following should be investigated further: medullary thyroid carcinoma in all groups but especially in aging Wistar-derived (WAG)/Rij females; carcinomas of the ureter and bladder in aging female and male Brown Norway (BN)/Bi rats. Multiple endocrine tumors in all groups of aging rats; aortic body lesions and tumors in aging WAG/Rij females; granular cell tumors in the brain of aging BN/ Bi, WAG/Rij and F1 rats; and the relatively high incidence of age-associated metastatic cancers in BN/Bi females compared to the other groups. Among these are the earlier mortality of WAG/Rij males and the possibility that it is the result of "premature" aging; the earlier onset of thymic atrophy in WAG/ Rij males and its possible link to the earlier onset of age-associated lesions and earlier mortality. The epithelial cell proliferation in the thymus of aging BN/Bi females and the possibility that these epithelial cells are producing a thymic hormone or hormones.
