Ovarian clear cell carcinoma (OCCC) is a rare histological subtype of epithelial ovarian cancers (EOCs), with an incidence, among EOCs, of 4–12% in western countries and a higher ratio of over 20% in Japan. Histologically, EOCs are classified into serous, mucinous, endometroid, clear cell and undifferentiated subtypes. David Winkler at Europital discusses the fact that ovarian cancer is already the leading cause of death among gynaecological malignancies in the US; in addition, the OCCC subtype presents a lower response rate to traditional platinum-based chemotherapy and is generally associated with poorer prognosis across all stages compared to other EOC subtypes.