Evolution of the concept and termiology of borderline ovarian tumours

Abstract

The borderline category of ovarian tumours was established in the early 1970s because of the observation that a group of proliferative epithelial ovarian tumours lacking invasion that generally behaved in a benign fashion occasionally pursued an indolent malignant course. Over the last 25 years, a large database on these tumours has been accrued. Recent studies suggest that the borderline group can now be subclassified into benign and malignant neoplasms. The survival for patients with serous borderline tumours confined to the ovaries is virtually 100%. Patients with ovarian serous borderline tumours with invasive peritoneal implants have a 34% mortality rate; therefore, these cases are classified as low grade carcinomas. Micropapillary serous carcinoma, a distinctive neoplasm that fails to display unequivocal evidence of invasion and therefore has been included in the borderline category, is strongly associated with invasive implants and recurs as invasive carcinoma. After these neoplasms with invasive implants are excluded from the group of tumours classified as borderline, the remaining advanced stage serous borderline tumours (those with non-invasive implants) have a disease-specific survival rate of nearly 100% and should be considered benign. In a similar fashion, the vast majority of mucinous borderline tumours reported to display aggressive behaviour have been associated with the clinical syndrome of pseudomyxoma peritonei. It is now clear that pseudomyxoma peritonei is a condition of appendiceal origin in virtually all cases. In addition, there is a small group of mucinous carcinomas typically from the pancreas and biliary system that present with relatively bland-appearing metastases to the ovaries that closely simulate mucinous borderline tumours. Once these metastatic carcinomas and mucinous tumours associated with pseudomyxoma peritonei are removed from the borderline category, the remaining mucinous borderline tumours are always confined to the ovaries and have a benign behaviour. Finally, review of the literature indicates the other epithelial types of borderline tumours (endometrioid, clear cell and transitional cell) behave in a benign fashion. Since borderline tumours can now be classified into benign and malignant types, the borderline category has no further utility and can be abandoned. This will be of great benefit to patients and clinicians, and will also help in more clearly focusing research efforts on ovarian cancer.