Among the 87 HCC tissues at stages II–IV, 78 (89.66%) showed positive staining of Syncytin-1, whereas only 6 of 16 (37.50%) HCC tissues at stage I were Syncytin-1 positive (p < 0.001; Fig. 2a, Table 1). Here, ERVW-1 is linked to hepatocellular carcinoma.