Pathology of borderline (low malignant potential) ovarian tumours.

Recent studies suggest that the borderline group of ovarian tumours can be subclassified into benign and malignant neoplasms. The survival for patients with serous borderline tumours confined to the ovaries is virtually 100%. Patients with serous borderline tumours with invasive peritoneal implants, and with micropapillary serous carcinomas (a distinctive neoplasm previously included in the borderline category), have a 30-40% mortality rate and therefore these tumours are classified as carcinomas. After these neoplasms are excluded, the remaining advanced stage serous borderline tumours (those with non-invasive implants) have a survival rate of nearly 100% and should be considered benign. Similarly, nearly all mucinous borderline tumours reported to display aggressive behaviour have been associated with pseudomyxoma peritonei, a condition now known to be of appendiceal origin. The remaining mucinous borderline tumours are always confined to the ovaries and have a benign behaviour. Since borderline tumours can now be classified into benign and malignant types, the category has no further utility.