**6. Ovarian clear cell carcinomas (OCCCs)**

Ovarian clear cell carcinomas comprise 10–12% of ovarian carcinomas with relatively high prevalence in young women of East Asian origin [121]. They are frequently associated with endometriosis lesions (50–74% of the cases) and/or clear cell benign (adenofibroma) or borderline tumours, pathologic entities with *PIK3CA* and *ARID1A* precursor genetic alterations [122]. They present mostly as unilateral mass in clinical stage I or II [5] and are considered a high-grade malignancy, although stage I patients have a favourable prognosis. Advanced-stage patients are related to poor clinical outcomes due to chemoresistance. Predisposition risk factors are late menopause, Lynch syndrome and expression of the genetic locus *HNF1B* through epigenetic mechanisms [122]. Lynch syndrome-associated OCCCs or tumours with MMR deficiency are correlated with long survival due to putative tumour immunogenicity [123].
