TK1 and hepatocellular carcinoma: Use the GEPIA database to verify 19 extracted core genes (KIF2C, CDC20, TPX2, TK1, CDKN3, CENPF, TOP2A, TRIP13, CDCA5, ASPM, MELK, NCAPG, PRC1, HJURP, AUPKA, KF20A, KIF4A, PTTG1, CCNA2, MCM2) Expression levels in HCC patients and normal subjects.