BACKGROUND: Data on unrecognized liver cirrhosis in patients with hepatocellular carcinoma (HCC) are derived mainly from cohorts with a risk of selection bias.OBJECTIVES: In a population-based cohort study we aimed to determine the proportion, characteristics, and prognosis of HCC in patients with unrecognized cirrhosis.METHODS: Using the Swedish quality register for liver cancer and other nationwide registers, we identified all adults with HCC in Sweden between 2012 and 2018 (n = 3,473).RESULTS: The final study cohort comprised 2670 patients with established cirrhosis, of which 1033 (39%) had unrecognized cirrhosis at HCC diagnosis. These patients were more often male, older, and had larger tumors, multinodular cancer, portal vein thrombos...