AIM:To detect the micrometastasis of gastric carcinoma inperipheral blood circulation using immunomagnetic beadssorting technique and RT-PCR technique,and to discuss itssignificance and the difference between the two methods.METHODS:Density gradient centrifugation was used toisolate mononuclear cells from peripheral blood,immunomagnetic beads sorting technique and RT-PCRtechnique were used to detect the disseminated carcinomacells.HE,immunocytochemical and immunofluorescencestaining were also used to identify the characteristics of thecells separated with immunomagnetic beads sorting technique.RESULTS:Cells expressing cytokeratin were separated andenriched from the peripheral blood specimens of patientssuffering from gastric carcinoma or chronic gastritis.After HEstaining,two kinds of cells with little cytoplasm were found.Majority of these cells had small and round nuclei,evenchromatins and the thickness of nuclear membrane wasnormal.Immunohistochemical staining indicated that therewere CD34 and CD45 expression on the cell membrane ofthis kind of cells and these cells also showed expressed humantelomerase reverse transcriptase by immunofluorescencestaining,but the expression of carcinoembryonic antigenwas absent.So,these cells might hematopoiesis precursors.Another kind of cells had larger and abnormal nuclei withthicker nuclear membranes.Massed chromatins and poly-nucleoli were found in the nuclei.These cells expressed humantelomerase reverse transcriptase and carcinoembryonicantigen,but CD34 and CD45 were not found on the cellmembrane.So,these cells were considered as gastriccarcinoma cells escaping from the original focuses andexisting in the peripheral blood circulation.Carcinoma cellswere found in 25 of 60(41.7%) specimens of peripheralblood from patients with gastric carcinoma,while there wereno such cells separated from the blood specimens of chronicgastritis patients.The difference of positive rates ofdisseminated carcinoma cells between two groups wasmarkedly significant (P<0.005).The expressions of CK20mRNA in peripheral blood specimens were examinated withRT-PCR.CK20 mRNA was detected from 32 of 60(53.3%)peripheral blood specimens in the group of gastric carcinomapatients,while none of the specimens from patients sufferingfrom chronic gastritis had CK20 mRNA.Significant differencewas also found between two groups (P<0.005).Statisticanalyses also showed that there was a significant difference between the positive rates of two methods in detecting thedisseminated carcinoma cells from the peripheral bloodcirculation of gastric carcinoma patients (P<0.05).CONCLUSION:The results demonstrated that there weredisseminated carcinoma cells in the peripheral bloodcirculation of some patients with gastric carcinoma.Disseminated carcinoma cells can be detected from theperipheral blood samples with immunomagnetic beadssorting technique and RT-PCR technique.The positive rateof RT-PCR technique is higher than that of immunomagneticbeads sorting technique in detecting micrometastasis. AIM: To detect the micrometastasis of gastric carcinoma inperipheral blood circulation using immunomagnetic beadssorting technique and RT-PCR technique, and to discuss itssignificance and the difference between the two methods. METHODS: Density gradient centrifugation was used to isolate mononuclear cells from peripheral blood, immunomagnetic beads sorting technique and RT-PCRtechnique were used to detect the disseminated carcinoma cells. HE, immunocytochemical and immunofluorescence staining also used to identify the characteristics of the cells separated with immunomagnetic beads sorting technique. CellsULTS cytokeratin were separated andenriched from the peripheral blood specimens of patientssuffering from gastric carcinoma or chronic gastritis. After HE arresting, two kinds of cells with little cytoplasm were found. Majority of these cells had small and round nuclei, evenchromatins and the thickness of nuclear membrane was normal. Immunohistochemical staining indicated that therewe re CD34 and CD45 expression on the cell membrane of thymus of cells and these cells also showed expressed human telomerase reverse transcriptase by immunofluorescence staining, but the expression of carcinoembryonic antigen was absent. These cells might hematopoiesis precursors. Another kind of cells had larger and abnormal nuclei withthicker nuclear membranes. Massed chromatins and poly-nucleoli were found in the nuclei. These cells were expressed humantelomerase reverse transcriptase and carcinoembryonicantigen, but CD34 and CD45 were not found on the cellmembrane.So, these cells were considered as gastriccarcinoma cells escaping from the original focus andexisting in the peripheral blood circulation .Carcinoma cellswere found in 25 of 60 (41.7%) specimens of peripheralblood from patients with gastric carcinoma, while there wereno such cells separated from the blood specimens of chronic gastritis patients. The difference of positive rates of isseated carcinoma cells between two groups wasmarkThe expressions of CK20 mRNA in peripheral blood specimens were examined with RT-PCR. CK20 mRNA was detected from 32 of 60 (53.3%) peripheral blood specimens in the group of gastric carcinomapatients, while none of the specimens from patients sufferingfrom chronic gastritis had CK20 mRNA. Significant difference was also found between two groups (P <0.005) .Statisticanalyses also showed that there was a significant difference between the positive rates of two methods in detecting thedisseminated carcinoma cells from the peripheral blood of gastric carcinoma patients (P <0.05). CONCLUSION: The results demonstrated that there weredisseminated carcinoma cells in the peripheral blood circulation of some patients with gastric carcinoma. Disseminated carcinoma cells can be detected from the peripheral blood samples with immunomagnetic beadssorting technique and RT-PCR technique. The positive rate of RT-PCR technique is higher than that of immunomagneticbeads sorting tech nique in detecting micrometastasis.