[Histological studies of multiple subperitoneal nodules produced by prolonged administration of estrogen (author's...

It has been reported that multiple peritoneal fibroids were produced in guinea pigs treated with large doses of estrogens, and the nodules regressed when the steroid stimulant was discontinued. Recently, these experimental nodules were considered to be simulating the disseminated pattern of Leiomyomatosis Peritonealis Disseminata (LPD). Although these experimental nodules were considered to be composed of fibroblasts by light-microscopic studies, LPD was verified to be composed of smooth muscle by electronmicroscopic studies. Therefore, it is indispensable to study these experimental nodules by electronmicroscopy, when we discuss about the similarities between experimental nodules and LPD. Guinea pigs were treated with various doses of estradiol benzoate (E) [40, 80, 100, 200 microgram/day, thrice a week, intramuscular injection]. After treatment for three months, every dose of E produced the lesions simulating the disseminated pattern of LPD: multiple nodules in various sizes, scattered on the surface of the uterine horn, peritoneum, spleen and pancreas, and in the omentum and mesocolon. Ultrastructurally, the nodules were composed of the cells resembling fibroblast. We conjectured that estrogen differentiates and proliferates the cells of the features of fibroblast-like cells from subcoelomic mesenchyme, resulting in the production of multiple superitoneal nodules simulating the disseminated pattern of LPD.