Microsatellite instability in synchronous gastric carcinomas

Synchronous gastric carcinomas are found in 4% to 10% of all gastric carcin omas, and the tumor multiplicity is believed to be related to genetic predi sposition. To investigate the role of mismatch repair error in synchronous gastric carcinomas, we analyzed the microsatellite instability (MSI) status of 101 cancers from 48 gastrectomy specimens and compared them with 149 so litary gastric carcinomas. Multiple synchronous gastric carcinomas are char acterized by slightly older age, predominance in males, early stage and low er lymph node metastasis. Among the 48 cases, 8 (18 lesions) were associate d with a gastric adenoma (type I) and 40 (83 lesions) were not associated w ith a gastric adenoma (type II). The MSI+ rate was 50% in the type I and 8. 4% in the type II synchronous gastric carcinomas (p < 0.001), while that of solitary gastric carcinomas was 9.4%, In addition, the frameshift mutation rates of the TGF-<beta>RII, BAX and hMSH3 genes in the type I synchronous carcinomas were higher than those in the type II synchronous carcinomas. Th ese findings indicate that a defect in the mismatch repair system might pla y a role in the carcinogenesis of a minor subset of multiple gastric carcin omas associated with adenomas, (C) 2001 Wiley-Liss, Inc.