CD81 and neoplasm: Our search identified the following: 1) TOP2A, CDKN2A, and APOE, which are involved in tumor growth, recurrence, and metastasis; 2) STAT1, which may be involved in metastasis of tumor through the p38 MAPK signaling pathway; 3) CD81, C3, and RAC1, which may promote tumor progression through the PI3K signaling pathway; and 4) other proteins, such as ALB, AFP, GC, LTF, SOD2, and NDRG1, which are involved in tumor metastasis.