Ovarian borderline tumors have also been referred to as “tumors of low malignant potential” or “atypical proliferative tumors”; however, “borderline tumor” is the preferred terminology. Borderline tumors exhibit epithelial proliferation and cytologic atypia, beyond that acceptable for a benign neoplasm, but do not exhibit the destructive growth seen in carcinomas. Approximately 15% of all epithelial ovarian neoplasms are borderline tumors and the majority (~70%) are stage I at diagnosis.
Serous and mucinous borderline ovarian tumors are the two most common types, while endometrioid, seromucinous, Brenner, and clear cell borderline ovarian tumors are much less common. Seromucinous is a confusing name, but merely refers to the mixed epithelial types present (i.e., serous, mucinous, endometrioid, etc.). The “seromucinous” subtype of borderline tumor is officially included in the most current WHO classification and like all the histotypes of borderline tumor other than serous, is almost always associated with a benign course.
Surgery for borderline ovarian tumours (BOT) is often performed in the community as they commonly arise in young women with a low index of suspicion of cancer. Detailed operative reports should describe all peritoneal surfaces in the pelvis and upper abdomen, contralateral ovary, omentum, and adjacent structures. When these findings are adequately documented, patients may not need repeat surgical staging procedures. Washings and unilateral cystectomy or USO can be considered for young women wishing to maintain childbearing. Research suggests cystectomy for BOT is associated with increased reoperation rate e.g., for subsequent cystectomies, or unilateral salpingo-oophorectomies, but does not negatively impact survival. Staging for BOT has evolved in the last decades, recognizing that lymph node metastases are exceedingly rare, and the most common distribution of disease is in the ovaries, adjacent pelvic structures, peritoneal fluid and/or omentum. Thus, modern staging procedures involve sampling these areas. In women who did not have this staging performed at initial operation, then re-operation is warranted unless there are significant co-morbidities. Women who are peri-or postmenopausal should consider removal of both ovaries, omental sampling and washings. In patients with pathology confirmed serous BOT without evidence of carcinoma, extraovarian disease, or invasive implants, surgery results in cure with very low risk of recurrence. Discussion with one of the BC Cancer team members or electronic triage for review of operative report and pathology can be requested. However, formal appointment for patients with confirmed stage I BOT is rarely needed. Additional surgery may be recommended in individuals with: (1) micropapillary component, as there is an increased risk of invasive extraovarian implants; (2) advanced stage disease or residual tumor. Post-operative systemic treatment, e.g., chemotherapy or hormonal, is recommended only for women with invasive implants. Follow-up is recommended at 6-month intervals, decreasing to yearly after the 2nd year from surgery.
Patients with BOT should not be referred to the Hereditary Cancer Program as there is no known hereditary predisposition to these.
