Aromatase inhibitors prevent spontaneous granular cell tumors in the distal female reproductive tract of Sprague-Dawley rats

We recently established diagnostic criteria for granular cell changes in th e distal female reproductive tract of rats. In a review of control animals from 9 carcinogenicity studies, we found that approximately 23% of animals had granular cell alterations. Because estrogen may play a role in the path ogenesis of granular cell alterations, we reviewed tissue sections from car cinogenicity studies with 2 aromatase inhibitors and found compound-related decreases in the incidence of granular cell changes. Since these aromatase inhibitors selectively prevent the conversion of androgenic steroids to th e corresponding estrogens, these data further suggest that estrogen may pla y a role in the pathogenesis of granular cell tumors of the reproductive tr act of rats.