Thymidine kinase-1 (TK1), lysyl oxidase (LOX), lysine demethylase 5B (KDM5B), proteasome 26S subunit non-ATPase 4 (PSMD4), and nuclear factor erythroid 2-like 3 (NFE2L3) genes are implicated in relapse and poor prognosis of patients with breast cancer. The gene discussed is TK1; the disease is breast cancer.