Many studies indicate that tumor markers CEA and CA 19-9 collected from the peritoneal cavity can be a reliable indicator of peritoneal metastasis and prognosis in patients with gastric cancer [14,27,28], and, according to a study by Li JK et al., determination of pCEA compared to intraoperative cytology is a more sensitive and reliable indicator of peritoneal metastasis and prognosis in patients with gastric cancer [29]. The gene discussed is CEACAM5; the disease is gastric cancer.