Borderline tumours of the ovary: A 37-year experience at a tertiary referral centre.

Introduction: Borderline ovarian tumours (BOT) are a common epithelial ovarian tumours. Typically diagnosed at an early stage with a good prognosis, many BOT are treated conservatively. Recurrence is common. This update to our last audit in 1997 represents one of the largest audits of BOT to date.

Materials and methods: All patients with BOT managed at 'the hospital' from 1984 to 2021 were included. Expert pathology review was available.

Results: There were 549 cases included. The recurrence rate was 5% (n = 29/549) with 1.4% (n = 8/549) undergoing malignant transformation. Three of the eight women who recurred as cancer died from their disease. Frozen section was predictive of histologic diagnosis in 92% (n = 55/60) of serous tumours (SBOT), but only 62% (n = 54/87) of mucinous tumours (MBOT). In MBOT where the appendix appeared normal intra-operatively, it was histologically benign in all cases (n = 63). In SBOT, the recurrence rate was 5/23 (22%), 12/52 (23%), 1/29 (3%) and 3% (P = <0.01) for unilateral cystectomy, unilateral oophorectomy ± cystectomy, bilateral oophorectomy, and bilateral oophorectomy with hysterectomy, respectively, as index procedure. In MBOT this correlated to 2/20 (10%), 3/93 (3%), 0 and 1/58 (2%), respectively.

Discussion: This study describes important information correlating first surgical procedure and fertility-sparing surgery to recurrence and malignant transformation. For all BOT subtypes, fertility-preserving surgery increased the risk of recurrence and hysterectomy was not superior to removal of both ovaries. In MBOT, frozen section is of limited utility and the macroscopically normal appendix is very unlikely to be anything but benign, if MBOT is the true histologic diagnosis.