In a study by Lee et al. [31], they showed that the level of CEA in peritoneal fluid was significantly correlated with peritoneal cytology and the tumors’ histologic types, whereas the level of CA 19-9 showed a significant correlation with peritoneal metastasis, depth of primary tumor infiltration, distant metastasis, stage of disease, peritoneal cytology, and histological type. This evidence concerns the gene CEACAM5 and neoplasm.