Microsatellite analysis in serous tumors of the ovary

Thirty-four serous ovarian neoplasms were analyzed for microsatellite insta bility (MIN) and loss of heterozygosity (LOH) at 20 chromosomal loci of eig ht different chromosomes, including the map positions of the six known mism atch repair genes. Twelve of the 20 (60%) serous ovarian rumors of low mali gnant potential (LMP) and 13 of 15 (87%) samples of serous ovarian carcinom as, taken from 14 patients, showed LOH at one or more of the analyzed micro satellite: loci. In serous carcinomas, LOH of the dinucleotide repeat D7S52 1 was most frequent. Six of 20 (30%) LMP tumors were also affected by MIN a t more than one locus, whereas in the carcinomas MIN was found only sporadi cally (p < 0.025). No correlation between increased occurrence of MIN and L OH at the chromosomal loci of the known mismatch repair genes were discover ed for these LMP tumors. Although our observation regarding LOH frequency i n serous LMP tumors and serous carcinomas is compatible with the hypothesis that serous LMP tumors might represent precursor lesions of invasive carci nomas, the results concerning the occurrence of MIN suggest that the mechan isms of tumorigenesis of some tumors of LMP are distinct from those in inva sive serous carcinomas.