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

Purpose: In this study the effect of continuous stimulation of gonadotropin s on sex cord stromal tumors in the rat was examined. Methods: Sex cord str omal tumors were induced by transplantation of ovaries under the splenic ca psule of ovariectomized rats. Beginning 180 days after transplantation, the se tumors were taken out and cut into several pieces, which were then retra nsplanted (by isotransplantation) under the splenic capsule of 80 either in tact 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 di ffered 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, t hese tumors were defined as malignant. They could be kept in culture and al ways led to the development of metastases after retransplantation into othe r rats. Conclusion: Benign sex cord stromal tumors can show malignant growt h after transplantation. This study for the first time demonstrates that go nadotropins are involved in the induction of ovarian malignancies.