Whilst the patient’s tumour tissue (and also MTC-22 cells) exhibited a point mutation in ARID1A, we did not identify a mutation in PIK3CA but instead observed a point mutation in PIK3CB. To our knowledge, PIK3CB mutations in ovarian clear cell carcinoma have not been described in the literature; however, Robinson et al. reported that PIK3CB variants in 9 (6.0%) of a cohort of 150 patients with castration-resistant prostate cancer, and two exhibited the same mutation seen in the ovarian clear cell carcinoma patient analysed here, namely, PIK3CB (E1051K) [27]. The gene discussed is PIK3CB; the disease is Familial prostate cancer.