Wu C, et al. - Using a large-scale population-based cancer registry database, authors investigated the incidence, risk factors, and prognosis in those with primary hepatocellular carcinoma (HCC) and synchronous lung metastasis. Data of 33,177 HCC patients were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015. A greater risk of lung metastasis was linked to male sex, younger age, non-white race, unmarried status, uninsured status, raised alpha-fetoprotein, larger primary liver tumor size, positive lymph node status, synchronal bone or brain metastasis, and tumor poor pathological differentiation in the HCC cohort. They recorded 12.8% vs 15.3%, 4.0% vs 5.7%, and 1.6% vs 2.4% as the 1-, 3-, 5-year overall survival vs cancer-specific survival rates for HCC lung metastasis patients, respectively. Unfavorable prognosis factors were older age, unmarried status, poor tumor differential grade, and absence of surgery.