Here, we evaluated the prognosis of patients with HCC by measuring serum levels of ERBB2, which exhibits oncogenic activity as a major factor of ERBB receptors in the EGFR signaling pathway, and neuregulin 4 (NGR4), which has been evaluated in various carcinomas as a major ligand for ERBB4. The gene discussed is NRG4; the disease is hepatocellular carcinoma.