A total of 40 samples were collected from four groups of females: Ten plasma samples from patients with pathologically confirmed EOC (mean age, 47 (30 (link)–54 (link)) years), ten plasma samples from matched healthy individuals (HIs) (mean age, 40 (26 –65 (link)) years) eight EOC tissue samples (mean age, 47 (30 (link)–54 (link)) years) and eight benign ovarian (mean age, 40 (17 (link)–70 (link)) years) neoplastic tissue samples. No patients had been administered neoadjuvant chemotherapy and all patients had undergone primary cytoreductive surgery. All cases of OC were histologically diagnosed and classified in accordance with the World Health Organization criteria (7 (link)). For microarray analysis, the first eight samples with best qualified were used in each group; RNA samples extracted from tissues with RIN values >5 were chosen for microarray analysis and the total RNAs extracted from all serum samples were used. 10 samples per group were used for the validation step by RT-qPCR (Table I). The sample collection was performed at Istanbul University Medical Faculty Department of Obstetrics and Gynecology (Istanbul, Turkey) between January 1, 2015 and March 31, 2016. Peripheral blood was collected into EDTA tubes (5 ml) and immediately centrifuged at 3,500 × g for 15 min at 4°C. The serum supernatant was transferred to RNase-free tubes. Sample serum fractions were collected and stored at −80°C until needed. For the collection of tissue, after the routine surgical operation, ~500 mg tissue was deposited in a sterile centrifuge tube containing RNAlater™ stabilization and storage solution (Ambion; Thermo Fisher Scientific, Inc.), stored at 4°C overnight and then stored at −80°C until needed.