49 Background: Increasing evidence suggests that gastric malignancy may be a stem cell disorder. Methods: Using FACS analysis supported by ImageStream technique verification, various populations of bone marrow-derived stem cells (BMSCs), such as Lin-CD45-CD133+CXCR4+ very small embryonic/epiblast-like stem cells (VSELs), CD45-STRO-1+CD105+ mesenchymal stem cells (MSCs), Lin-CD45+CD133+ hematopoietic stem/progenitor cells (HSPCs), and CD34 +/ KDR +/ CD31 +/ CD45- endothelial progenitor cells (EPCs) were enumerated and sorted from peripheral blood samples of patients with gastric cancer (n = 23) and other gastric tumors (GISTs, NENs, lymphomas; n = 15) and control patients (n = 15). RT-qPCR analysis for the expression of cancerous, embryonic, and tissue trans-differentiation markers (Oct-4, Nanog, TFF-1, TFF-2, Lgr-5, BMI-1) in circulating VSELs was employed. The plasma levels of stromal-derived factor-1 (SDF-1), complement-derived anaphylatoxins/molecules (C3a, C5a, C5b-9/MAC), and interleukins (IL-6, IL-8, IL-17 and IL-23) were measured. Results: Significantly lower numbers of circulating HSPCs, and intensified peripheral trafficking of both VSELs and MSCs was observed in patients with gastric cancer, but not in those with other types of gastric tumors. In gastric cancer patients, the circulating VSELs presented higher gene expression of Oct-4, Nanog, Lgr-5, BMI-1, and TFF-1/2. The abnormal balance in the peripheral trafficking of BMSCs in patients with gastric cancer was not associated with the clinical stage of the disease or with the systemic levels of stromal-derived factor-1 (SDF-1), but correlated with the levels of C5b-9/MAC, IL-6, IL-8 and IL-23. Conclusions: Abnormal peripheral trafficking of BMSCs occurs in patients with gastric cancer, but not in those with other types of gastric neoplasms. Selected interleukins and complement cascade-derived molecules, but not SDF-1, seem to be significant players associated with this phenomenon (POIG.01.01.02-00-109/09 and IP2014003273).