Papillary adenocarcinoma of the stomach is a relatively uncommon histological type, and it is often detected in the early stage. We recently characterized the papillary type of gastric cancer and found frequent microsatellite instability and associated mutations. In this study we analyzed the centromere numerical abnormality (CNA) of 18 chromosomes (chromosomes 1-4, 6-12, 15-18, 20, X, and Y) in the papillary and papillotubular types of gastric cancer by a modified fluorescence in situ hybridization technique with microwave treatment. All 3 cases (100%) of papillary adenocarcinoma had high microsatellite instability (MSI-H), and low CNA, and 41% (7 cases) of the 17 cases of papillotubular adenocarcinoma exhibited MSI-H and all 7 cases had low CNA. Further 8 cases (47%) had extensive CNA. In these 15 cases, all the MSI-H cases had lower CNA, and low microsatellite instability (MSI-L) and MSS cases had higher CNA. The remaining two cases showed low CNA and MSI-L and MSS. These profiles were different from those of tubular type gastric cancer, which always had extensive CNA and no MSI. Although the numbers of the cases in this series are limited, our data may suggest that a modest CNA may be another characteristic of gastric cancer with papillary structure.

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