Dear Colleagues,

Ovarian tumors consist of a wide diversity of histologic types, with non-epithelial ovarian tumors being the least frequent. As a result, large-scale clinical trials are challenging to conduct, and there is a need for evidence-based treatment strategies. We completed a retrospective study of 1,426 cases of granulosa cell carcinoma from the 75,241 ovarian tumors registered with the Japanese Society of Obstetrics and Gynecology (Ebina Y et al., Clinicopathological characteristics and prognostic factors of ovarian granulosa cell tumors: A JSGO-JSOG joint study. Gynecol Oncol. 2021 Nov;163(2):269–273.) However, so far there have been limited opportunities to analyze this data. This special issue will gather the latest clinical findings on the rare ovarian tumors mentioned below, thus providing insight into the gaps not covered by evidence-based treatment. The main histological types targeted include granulosa cell tumors and other sex cord-stromal tumors, as well as immature teratomas and other germ cell tumors. Additional rare ovarian tumors will also be considered for this program.

We also intend to share information about rare ovarian tumor types that present a unique picture in terms of treatment, diagnosis and clinical course. We hope this Special Issue will provide a forum for sharing knowledge about such tumors.

Prof. Dr. Yasuhiko Ebina
Guest Editor