Rare ovarian tumors: an update on diagnosis and treatment

Rare ovarian cancers occur frequently. Almost half of ovarian malignancies relate to several different ‘rare’ histotypes, according to the World Health Organization. The most common tumors are epithelial tumors, including high grade serous carcinomas, the presumed ‘frequent ovarian cancers’, together with low grade serous, mucinous, endometrioid, clear cell, and carcinosarcomas. Sex cord stromal tumors and germ cell carcinomas define two other groups of different subtypes, and small cell carcinomas are an independent high grade subtype closely related to the family of rhabdoid tumors. All of these cancers are primary ovarian cancers, classified by the International Federation of Gynecology and Obstetrics. However, the tumor subtypes display various epidemiologic, clinical, pathological, prognostic, and therapeutic characteristics. Because of the scarcity of data, current understanding of each subtype is limited and treatment has generally been derived from the more common tumor types. The aim of this article is to review the current literature on rare ovarian malignancies.