The relationship between gastric cancer cells circulating in the blood and microsatellite instability positive gastric carcinomas

Background: Cancers characterized by microsatellite instability may be biologically different from their counterparts with stable microsatellite sequences. Circulating cancers cell present in blood prior to surgery may constitute an adverse prognostic finding. Aim: To correlate these two phenomena with morphological features and survival in advanced gastric cancer. Methods: We examined 76 cases of resected sporadic, advanced gastric cancer by means of routine morphology and a panel of microsatellite markers. Sixty-six cases were screened for presence of cancer cells circulating in blood prior to the surgery using combined morphological and immunocytochemical approach. Results: Twenty-one (27.6%) cases demonstrated microsatellite instability in at least one locus. Among them 11 (14.5%) showed microsatellite instability in more than 30% (4/12) examined loci, and they were therefore designated as replication error positive (RER+). Circulating cancer cells were detected in 2/19 microsatellite instability and in 11/47 remaining cases (difference not significant). The survival of the microsatellite instability cases was significantly better. The presence of circulating cancer cells did not correlate with survival. Conclusion: It is possible that the microsatellite instability status, but not circulating cancer cells, constitutes a prognostic predictive factor in advanced gastric carcinoma. Confirmation of this hypothesis requires continuation of patient follow-up.