Microsatellite instability (MSI) testing is tricky in gynaecological cancers (GC). Thus, we aimed to describe the instability patterns to improve MSI test interpretation in sporadic and hereditary GCs. Ninety-five cases, including uterine and ovarian cancers, with known genetic and immunohistochemical (IHC) features, were analysed for MSI by a mononucleotide repeats pentaplex (MRP). We identified 13 ambiguous cases that did not fully meet MSI criteria (‘borderline’ cases, B-MSI), which were mainly represented by MSH2/MSH6-deficient and Lynch syndrome cases. Also, we evaluated nine additional loci of candidate MSI markers that did not improve the detection of MSI cases, but might be useful for discordant or borderline samples. In conclusion, although MSI and IHC test are highly concordant, a subset of ambiguous MSI cases deserves a careful interpretation in particular when MSH2/MSH6 are involved. RPL22 and SRPR testing may be useful to integrate MRP panel for the analysis of critical cases.
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LL and NS contributed equally.
Handling editor Runjan Chetty
Contributors LL, NS, CR, MGT, FS, DF: conceived and designed the experiments. LL, IWC, LC, RC: performed the experiments. LL, NS, AMC, DF: analysed the data. LL, NS, DF: wrote the paper. DF: supervised the research project and paper drafting.
Funding The study has received financial support from Epigenomics Flagship Project—EPIGEN (to D. Furlan; project # 08934412).
Competing interests None declared.
Ethics approval This study was performed according to the clinical standards of the 1975 and 1983 Declaration of Helsinki and was approved by our Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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