Microsatellite instabilities in gastric cancer patients with multiple primary cancers

To answer whether microsatellite instability (MSI) can serve as a molecular marker for the risk-assessment of the development of multiple cancers, 26 tumors from 10 gastric cancer cases with multiple primary cancers were inve stigated. Six out of 10 cases revealed MSI in one or more cancer DNA. Signi ficant statistical association was observed between MSI positive gastric ca ncer and cancer multiplicity (chi(2) test, P<0.05). The complicated primary tumors in MSI-positive cases arose in colorectum, urogenital tract and ova ry, which mimicked the tumor spectrum of hereditary non-polyposis colorecta l cancer (HNPCC). On the other hand, most of the multiple cancers in MSI ne gative group were found synchronously and limited to the digestive organs. These observations suggest that MSI test on gastric cancer may be considere d as a good marker for the assessment of multiple cancer development especi ally in the sites where tumors of HNPCC usually develop.