Peritoneal lesions in guinea pigs treated with hormones

Foci of peritoneal fibrosis frequently occur with ovarian neoplasms, especially those of epithelial type, usually in association with foci of metastatic tumor or implants. However, in the absence of the latter, the presence of fibrosis cannot be clearly explained. To find an explanation for this phenomenon, we investigated the development of hormone-dependent peritoneal changes in guinea pigs. Of the 59 guinea pigs studied, 49 received one of the following hormones or hormone analogs: estradiol, diethylstilbestrol (DES), testosterone, estrone, Megace, human chorionic gonadotropin, Norethin, clomiphene, luteinizing hormone, dienestrol, hexestrol, and tamoxifen, over a period ranging from 3 to 9 months. Ten guinea pigs received sterile water (control cases). Multiple peritoneal fibrous plaques 1 to 7 mm in greatest dimension were found in 5 of 7 guinea pigs that received estradiol, 6 of 8 treated with DES, and 2 of 2 that received hexestrol and estrone. The largest lesions (fibrous polyps up to 1.2 cm in greatest dimension) were seen in those that received estrone; however, this hormone was poorly tolerated, as two of the animals that received it died after 1 and 2 months, respectively. Because DES was the best-tolerated hormone, we administered it to five additional guinea pigs for 12 months. All five developed fibrous plaques; three of them also developed peritoneal fibroleiomyomas. We conclude that estrogens can induce the development of fibrous plaques in the peritoneum and when they are administered for a long period of time they also induce the development of smooth muscle nodules. This finding is relevant to understanding the pathogenesis of both fibrous lesions associated with ovarian tumors and peritoneal leiomyomatosis.