['The aim of the study was to define the clinical characteristics and outcome of patients found to have undetected hepatocellular carcinomas (HCC) at liver transplantation. Patients who underwent liver transplantation and were unexpectedly found to have a HCC despite prior workup showing normal alpha-fetoprotein levels and/or no visible radiological lesion were defined as having an undetected HCC.', 'Thirty-two of these patients had a histological diagnosis of HCC in the explanted liver. Undetected HCC was defined as a carcinoma found only on pathological evaluation of the explanted liver, with a pre-OLT workup showing a normal serum alpha-fetoprotein (AFP) level (<20 ng/mL) and/or no suspicious lesion on preoperative radiological evaluation.', 'Nine patients had a tumor that met the criteria for an undetected HCC. The most common cause for transplantation was cryptogenic cirrhosis (44.4%). Tumor size was 2 cm or less in all patients, vascular invasion was detected in 11.1% of the patients, and tumor, node, metastasis (TNM) classification was stage I in 77.8%. Eight patients (88.9%) remained alive at the cessation of the analysis with a mean follow-up of 60 +/- 30.4 months. There was no tumor recurrence in any patient. Statistical analysis showed significant differences between undetected and detected HCCs when causes of pretransplantation liver disease, peak AFP level, tumor size, number of tumors, presence of vascular invasion or pathological differentiation were compared. Undetected HCCs were associated with a better survival rate after liver transplantation (p = 0.008).'] Is undetected hepatocellular carcinoma in patients undergoing liver transplantation : associated with favorable outcome?