Introduction/Background*Immature teratomas are rare germ cell ovarian tumours occuring in about 1% of ovarian cancers. Growing Teratoma Syndrome (GTS) is a rare clinical situation where seemingly successful chemotherapy is followed by a rapid tumor progression, while tumour markers normalize. Despite radiological progression, the phenomenon is characterised by the maturation of the teratoma, and in most cases there is hardly any immature component left. In these rare cases radical surgical treatment is usually effective and can lead to complete recovery.

Result(s)*A joint working group of the Department of Gynecology and Department of Genitourinary, Medical Oncology and Clinical Pharmacology of the National Institute of Oncology, Hungary diagnosed three immature ovarian teratoma cases with extended pelvic/abdominal tumor mass which showed progressive growth during and following chemotherapy. In all three cases, we had to perform multivisceral cytoreductive surgery with peritonectomy leading to complete cytoreduction. All patients are currently tumor-free. Postoperative histological findings showed 80-100% maturation, one of them operated 19 years after the primary treatment.

Conclusion*By presenting these 3 patients, our goal is to raise awareness of the possibility of GTS and to emphasize the importance of adequate treatment.