To explore the potential therapeutic value of selenoproteins in tumor immunity, this review is based on the core hypothesis that “the mechanisms of ferroptosis resistance in cancer cells mediated by selenium and selenoproteins can be therapeutically targeted.” We focus on the process by which cancer cells in solid tumors synthesize key selenoproteins (such as GPX4) through selenium metabolism to establish a defense system against ferroptosis. The gene discussed is SELENOS; the disease is neoplasm.