Introduction/Background Ovarian clear cell carcinoma (OCCC) is a special subtype of epithelial ovarian carcinoma with unique characteristics and no specific tumour markers. Due to the inherent chemoresistance, there are no effective chemotherapy regimen for OCCC, resulting in the extremely poor prognosis of patients, especially at advanced stage. Therefore, the purpose of our research is to investigate the clinical characteristics and outcomes of ovarian clear cell carcinoma (OCCC) and to provide additional supporting evidence to aid in the clinical diagnosis and management.

Methodology This was a retrospective study investigating the clinical characteristics and survival outcomes of 87 patients with OCCC treated at The First Affiliated Hospital of University of Science and Technology of China (USTC), between January 2010 and March 2020. Survival analysis was also performed on 179 patients with OCCC diagnosed between 1975 and 2017, obtained from the Surveillance, Epidemiology and End Results (SEER) cancer registry database.

Results The median age of study participants was 49.28 ± 9.8 years old, with 74.71% diagnosed at an early stage. Median CA125 level was 607.26 IU/mL, with 23.94% having a normal CA125 level. 16 patients (18.39%) had co-existing endometriosis and 8 patients (9.2%) had a preoperative history or developed postoperative complications of venous thromboembolism (VTE). Surgical staging procedures were performed on 65 patients and cytoreduction was performed on 22 patients, among whom 17 patients received optimal cytoreduction. 67 patients (77.01%) underwent lymphadenectomy, and only 3 (4.48%) were found to have positive lymph nodes. Positive HNF1β, and negative WT-1, ER, and PR are reliable immunohistochemical indicators of OCCC. Patients diagnosed at an early stage had higher 3-year overall survival (OS) (89.47% vs. 44.44%) and progression-free survival (PFS) rates (78.95% vs. 22.22%) than those with advanced stage OCCC at diagnosis. CA199 (P = 0.025) and ascites (P = 0.001) were significantly associated with OS, while HE4 (P = 0.027) and ascites (P = 0.001) were significantly associated with PFS. Analysis of data from the SEER database showed that the presence of positive lymph nodes is also an independent prognostic factor for OS (P = 0.001).

Conclusion OCCC often presents at an early stage and young age with a mild elevation in CA125 level. CA199, HE4, massive ascites and positive lymph node are independent prognostic factors for overall survival in OCCC.

Disclosures This work was supported by the National Natural Science Foundation of China (81872110, 81902632), National Key Research and Development Program (2018YFC1003900), Anhui Provincial Key Research and Development Program (1704a0802151). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. No conflicts of interest to disclose.