Résumé : Background: The development of a second primary tumor is a potential late side effect of radiotherapy. Particularly, an increased risk of secondary cancers, mostly of digestive or breast origin, has been observed in patients treated with high-dose radiotherapy for Wilms tumor (WT) in childhood. However, hepatocellular carcinoma (HCC) has been very rarely described as a potentially radiotherapy-induced tumor. We describe the case of a patient with an aggressive HCC 50 years after the treatment of a WT. Case presentation: A 49-year old man, treated at the age of 6 weeks for a right WT by a right nephrectomy and adjuvant radiotherapy, presented with a right abdominal mass. Imaging demonstrated a 100-mm tumor invading the inferior segment of the right liver, the right colon and the right psoas muscle. The patient had no previous history of liver disease, nor of alcohol consumption, and hepatitis serologies were negatives. Biopsy demonstrated a poorly differentiated tumor of unknown origin. A panel of tumor markers was negative. Explorative surgery has been performed allowing en bloc R0 tumor resection, including resection of segments VI and VII of the liver, right hemicolectomy and resection of the anterior sheet of the right psoas muscle. Pathological examination revealed a poorly differentiated HCC. No signs of cirrhosis or chronic liver disease were observed in the non-tumor liver. Twenty weeks after surgery, the patient developed a multifocal tumor recurrence that was treated with intra-arterial 90Yttrium radioembolization. Conclusion: In this case, the absence of risk factors for HCC, such as cirrhosis, viral hepatitis and chronic liver disease, highly suggests the development of HCC to be related to previous high-dose radiation therapy given for a right WT to a field involving the inferior part of the liver. This observation shows radiotherapy to/near the liver, particularly in childhood, to be a potential risk factor for HCC, stressing the need for a long-term specific follow-up in patients irradiated in childhood.