Expression of keratin 19 is related to high recurrence of hepatocellular carcinoma after radiofrequency ablation. 
Keratin (K) 19 positivity has been reported to be a useful predictive marker for recurrence in patients with hepatocellular carcinoma (HCC) who have undergone hepatic resection.  We investigated the clinical usefulness of K19 positivity in patients who had received curative radiofrequency ablation (RFA).  We retrospectively evaluated the clinicopathological features, including imaging and K19 expression, in 246 patients with HCC who were within the Milan criteria and had received curative RFA.  Using a two-step insertion method, tumor biopsies were obtained just prior to RFA and were evaluated histologically.  Tumor seeding due to liver biopsy and RFA was not observed.  Ten patients (4.1%) had K19-positive HCC.  Imaging findings were similar between K19-positive and -negative HCC (p = 0.187).  Nine out of 10 patients (90%) who had K19-positive HCC had recurrence of HCC after RFA, and intrahepatic recurrences were observed within 12 months in 6 out of 10 (60.0%).  K19 positivity was a significant risk factor for recurrence (p < 0.0001) and early recurrence (<1 year after RFA; p =0.012).  K19 expression (p = 0.016) was an independent risk factor for tumor status exceeding the Milan criteria after RFA.  Expression of K19 is related to high recurrence of HCC after curative RFA.