CEACAM5 and signet ring cell carcinoma: As summarized in Table 2, no surgery of primary cancer (P < 0.001), no radiation (P < 0.001), M1b stage (P < 0.001), elevated CEA level (P < 0.001), older age (P < 0.001), unmarried status (P < 0.001), signet ring cell carcinoma (P < 0.001), undifferentiated grade (P < 0.001), larger tumor size (P < 0.001) and T1/4 stage (P < 0.001) were found to be risk factors for mRC patients’ survival by univariate log-rank test.