Role of gonadotropins in malignant progression of sex cord stromal tumors produced by sequential auto- and isogenic transplantation of ovarian tissue in ovariectomized rats

Purpose: In this study the effect of continuous stimulation of gonadotropins on sex cord stromal tumors in the rat was examined. Methods: Sex cord stromal tumors were induced by transplantation of ovaries under the splenic capsule of ovariectomized rats. Beginning 180 days after transplantation, these tumors were taken out and cut into several pieces, which were then retransplanted (by isotransplantation) under the splenic capsule of 80 either intact or ovariectomized rats. Results: Most of the tumor grafts grew up to a median size of 0.7 cm in ovariectomized rats. However, some of the tumors recovered from recipient rats that were retransplanted with donor tumors differed significantly from the others. Characterized by a high mitotic rate, nuclear atypia, size (up to 3.8 cm) as well as growth in intact animals, these tumors were defined as malignant. They could be kept in culture and always led to the development of metastases after retransplantation into other rats. Conclusion: Benign sex cord stromal tumors can show malignant growth after transplantation. This study for the first time demonstrates that gonadotropins are involved in the induction of ovarian malignancies.