Tumors of low malignant potential (i.e., borderline tumors) account for 15% of all epithelial ovarian cancers. Nearly 75% of these tumors are stage I at the time of diagnosis. These tumors must be recognized because their prognosis and treatment is clearly different from the frankly malignant invasive carcinomas.
A review of 22 series (953 patients) with a mean follow-up of 7 years revealed a survival rate of 92% for patients with advanced-stage tumors, if patients with so-called invasive implants were excluded. The cause of death was determined to be benign complications of disease (e.g., small bowel obstruction), complications of therapy, and only rarely (0.7%), malignant transformation. In one series, the 5-, 10-, 15-, and 20-year survival rates of patients with low malignant potential tumors (all stages), as demonstrated by clinical life table analysis, were 97%, 95%, 92%, and 89%, respectively. In this series, mortality was stage dependent: 0.7%, 4.2%, and 26.8% of patients with stages I, II, and III, respectively, died of disease. Another large study showed early stage, serous histology, and younger age to be associated with a more favorable prognosis. In contrast to the excellent survival rates for early-stage disease reported above, the Federation Internationale de Gynecologie et d'Obstetrique Annual Report (#21) included 529 patients with stage I tumors with a 5-year actuarial survival rate of 89.1%. Similarly, good survival was found in a large prospective study. Nonetheless, these survival rates are clearly in contrast with the 30% survival rate for invasive tumors (all stages).
The less common endometrioid tumor of low malignant potential should not be regarded as malignant because it seldom, if ever, metastasizes. Malignant transformation can, however, occur and may be associated with a similar tumor outside of the ovary; such tumors are the result of either a second primary or rupture of the primary endometrial tumor.
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- Kaern J, Tropé CG, Abeler VM: A retrospective study of 370 borderline tumors of the ovary treated at the Norwegian Radium Hospital from 1970 to 1982. A review of clinicopathologic features and treatment modalities. Cancer 71 (5): 1810-20, 1993.
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- Norris HJ: Proliferative endometrioid tumors and endometrioid tumors of low malignant potential of the ovary. Int J Gynecol Pathol 12 (2): 134-40, 1993.