It is clear that in the top ten genes in PPI network of CESC, ESCC, and LUSC, nine of them (BUB1, BUB1B, CCNA2, CCNB1, CCNB2, CDC20, CDC6, CDK1, and MAD2L1) are the same. The gene discussed is CCNA2; the disease is esophageal squamous cell carcinoma.