81 out of 84 (96.43%) Syncytin-1-positive HCC patients displayed HBsAg positivity in serum, whereas serum HBsAg positivity was found only 9 of 19 (47.37%) in Syncytin-1-negative HCCs (Fig. 2k). This evidence concerns the gene ERVW-1 and hepatocellular carcinoma.