title: Different types of microsatellite instability in ovarian carcinoma.
abstract: Microsatellite instability at mono- and dinucleotide repeats is the hallmark of the hereditary non-polyposis cancer syndrome (HNPCC) and is related to deficient DNA mismatch repair. In contrast, a distinct form of microsatellite instability at selective tetranucleotide repeats (EMAST or elevated microsatellite alterations at selected tetranucleotides) was described in several non-HNPCC cancer types. EMAST is probably unrelated to mismatch repair defects. We investigated the frequency of microsatellite instability at mononucleotide, dinucleotide and tetranucleotide repeats in a series of 75 ovarian carcinomas (53 serous and 22 non-serous). Microsatellite analysis was carried out using 5 mono- and dinucleotide markers from the National Cancer Institute Consensus Panel and 6 tetranucleotide markers, which have been reported as frequently unstable in the literature. High frequency of microsatellite instability (MSI-H) at mono- and dinucleotide repeats was observed in 9% and a low frequency (MSI-L) in 21% of serous carcinomas. MSI-H was detected in 4% and MSI-L in 18% of non-serous carcinomas. Nine percent of serous carcinomas showed instability at multiple and 9% at single tetranucleotide loci. All non-serous carcinomas were stable at tetranucleotide loci. In summary, EMAST (e.g., tumors with tetranucleotide instability without concomitant MSI-H) was observed in 13% of ovarian serous carcinomas. All EMAST positive tumors were of advanced stage. We conclude that EMAST occurs as a distinct form of microsatellite instability in ovarian cancer. EMAST seems to be particularly frequent in advanced serous carcinomas. Its clinical significance needs to be investigated.
authors.affiliation: Institute of Pathology, University of Basel, Switzerland. gsinger@uhbs.ch
authors.forename: Gad
authors.initials: G
authors.lastname: Singer
authors.forename: Thore
authors.initials: T
authors.lastname: Kallinowski
authors.forename: Arndt
authors.initials: A
authors.lastname: Hartmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dietmaier
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Wild
authors.forename: Peter
authors.initials: P
authors.lastname: Schraml
authors.forename: Guido
authors.initials: G
authors.lastname: Sauter
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mihatsch
authors.forename: Holger
authors.initials: H
authors.lastname: Moch
mesh_terms: D002277:Carcinoma / Q000235:genetics*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018895:Microsatellite Repeats; D010051:Ovarian Neoplasms / Q000235:genetics*