Microdissection-based mutational genotyping of serous borderline tumors of the ovary

Mutational changes in a number of genetic foci were studied in 12 serous borderline tumors (SBTs) of the ovary including 2 with a micropapillary pattern. The analysis was focused on chromosomal regions that have not been previously studied in these tumors. The findings were correlated with the morphology and the FIGO stage of the tumors. Six of the tumors were stage I, one was stage II, and five were stage III. Loss of heterozygosity analysis in each tumor was performed with a panel of 12 polymorphic markers on chromosomes 1p, 5q, 9p, 9q, 10q, and 17p. The ovarian tumors displayed allelic losses most frequently on 1p (83.3%), 9q (70%), and 17p (41.7%). In the extraovarian implants, allelic losses on 1p, 9q, and 17p were present in 66.7%, 75%, and 66.7% of cases respectively. In five of six cases, allelic losses were 88% concordant between multiple tumor sites. Only one case of stage III tumor displayed a discordant pattern of allelic loss at different tumor sites. Cumulative allelic losses did not show a statistically significant difference in stage I vs. higher stage disease. The pattern and cumulative allelic loss in the two cases with micropapillary architecture was similar to that of the other tumors. We report a high frequency of allelic loss on 1p and 9q that has not been previously reported in SBTs. Morphologically heterogenous areas including benign-appearing, typical borderline, and micropapillary areas had a similar pattern of allelic loss. Although the majority of SBTs seem to be monoclonal, a minor subset may be multiclonal in origin.