Carcinoembryonic antigen (CEA) and carbohydrateantigen 199 (CA199) are two commonly used serum tumor biomarkers forGC diagnosis but are challenged by low sensitivity and specificity.Extracellular vesicles (EVs) are membrane nanovesicles secreted byalmost all types of cells.2 The bioactivemolecules selectively packaged into EVs are considered promising biomarkersfor cancer liquid biopsy.3−5 However, the diagnostic accuracyof EVs is limited by their heterogeneity. This evidence concerns the gene CEACAM5 and cancer.