Evidence for a unifocal origin in familial ovarian cancer

The purpose of this investigation was to determine the pattern of loss of heterozygosity in multiple tumor sites from familial ovarian cancer cases. If ovarian cancer arises focally in one ovary and then metastasizes to other sites, a similar pattern should be seen in all tumor sites. However, if ovarian cancer arises multifocally throughout the peritoneal cavity, a different pattern of loss would be expected among the different sites.

The presence or absence of loss of specific alleles for 9 loci on chromosomes 1, 6, 11, 13, 16, and 17 was determined in multiple tumor sites from 12 familial ovarian cancer cases.

The frequency of loss of heterozygosity was as follows: chromosome 17 (100%), chromosome 13 (82%), chromosome 6 (80%), chromosome 16 (73%), chromosome 1 (57%), and chromosome 11 (22%). In every case an identical pattern was present for at least one locus. In four cases loss of the same allele was present in tumor from the ovary and all metastatic sites for all informative loci. In the remaining eight cases loss of the same allele for one to five (mean three) loci was detected.

The pattern of loss of heterozygosity in the 12 familial ovarian cancers included in this investigation favors a unifocal origin of disease. A dual primary origin could not be absolutely excluded in 3 cases. High frequencies on chromosomes 17q and 13 suggest that loss of whole or part of these chromosomes is important in ovarian carcinogenesis.