This book aims to become a useful tool in the field of gynaecological oncology providing the most up-to-date research on non-epithelial ovarian tumours, including the recent data on pathogenesis and the current strategies for diagnosis, treatment, and follow-up. The authors present and review important data on rare and various primary ovarian neoplasms such as the many subtypes of germ cell tumours, of the most important subtypes of Sex cord -Stromal tumours and the rare mixed forms of Germ cell and Gonadal Stromal tumours. Non-specific mesenchymal tumours of the ovary are reviewed, as well as Secondary neoplasms, metastatic to the ovary from various sites (extragenital and genital primaries).