Factors Affecting Recurrence in 165 Patients with Serous Borderline Ovarian Tumours: The Pattern of Micro-Invasion Is Main Prognostic Factor.

: The aim of this study was to evaluate the serous borderline ovarian tumours (BOTs), the recurrence rates, and the factors affecting recurrence. : A total of 165 patients diagnosed with serous BOT between 2004 and 2019 were included. The patients were evaluated in respect of age, preoperative CA125 levels, FIGO stage, tumour size, stromal micro-invasion, the presence of non-invasive implants, surgical procedures, and lymphadenectomy performed, or all that affects disease-free survival. : Early-stage BOT (stage I-II) was determined in 149 (90.3%) patients. Conservative surgery was performed in 57 (34.5%) patients. The non-invasive implantation was detected in 19 (11.5%) patients, and micro-invasion was determined in 31 (18.8%) patients. The median follow-up was 120 months, and recurrence was observed in 8 (4.8%) patients. The 5-year disease-free survival rate was 95.2%, and the 10-year disease-free survival rate was also 95.2%. Univariate analysis showed that elevated preoperative CA125 levels and the presence of micro-invasion were associated with poor disease-free survival outcomes. In the multivariate analysis, the presence of micro-invasion was the only independent poor prognostic factor (HR: 8.944, 95%CI: 2.060-38.833; p:0.003). : The micro-invasion was the main factor for recurrence in patients with serous BOT.