Furthermore, to analyze the prognostic factors for OS, retrospective analysis was performed, and data were obtained, including age at first PM, sex, size and number of initial HCC, serum alpha-fetoprotein level immediately before PM, recurrence or systemic metastasis of the primary tumor before detection of pulmonary metastasis, characteristics of pulmonary metastases (number, size, and pathologic findings), surgical procedures and approach, and number of PM. This evidence concerns the gene AFP and hepatocellular carcinoma.