Ovarian tumors of low malignant potential: Correlation of DNA index and S-phase fraction with histopathologic grade and clinical outcome

BACKGROUND. DNA ploidy and/or S-phase fraction have been used as biologic predictors of aggressive behavior in a variety of solid tumors, including ovarian carcinomas. Recently, attention has focused on borderline lesions to determine if flow cytometry plays a role in separating potentially aggressive tumors from those which will pursue a more innocuous course. METHODS. Paraffin-embedded tissue from 42 tumors with low malignant potential (LMP) were analyzed by flow cytometry (FC) to determine the DNA index (DI) and S-phase fraction (SPF). These results were then correlated with conventional pathologic parameters (size, nuclear grade, architecture, and mitotic index) and with clinical parameters (stage and age). Statistical analysis was carried out using the Fisher's Exact and Kruskal-Wallis tests. RESULTS. Thirty-five cases (83.3%) were diploid, while 7 cases (16.7%) showed aneuploid stemlines, with a mean DI of 1.2 (range: 1.1-1.4). The mean SPF was 3.5% for the diploid tumors and 4.5% for the aneuploid tumors. Serous tumors comprised 74% of our cases; the remainder were either mucinous or endometrioid tumors, Complex solid architectural patterns were found in 29 tumors whereas high nuclear grade was seen in 24. A mitotic rate (MR) of 0-3/10 high power fields was seen in 29 tumors (69%), with only 5 having 10 or more mitotic figures. Aneuploidy statistically correlated with higher stage (P < 0.009). Marginal correlation was seen with a larger tumor size (P = 0.06). SPF showed a direct linear correlation with MR (P < 0.001). Also, smaller SPF's were seen in the serous tumors versus the mucinous and endometroid group (P < 0.05). Two patients with diploid and one patient with aneuploid stemlines had recurrent disease during the follow-up period. CONCLUSIONS. DI and SPF correlated with some of the histologic parameters we evaluated. DI and SPF, however, could not predict which tumor(s) would behave in a more aggressive fashion.