Occurrence of a primary liver cancer with an unusual histologic appearance as a late Fontan complication.

The Fontan procedure is an open heart procedure performed in pediatric patients with a particular congenital cardiac anomaly known as a univentricular heart. The procedure is used to reroute the systemic venous blood from the inferior vena cava directly to the pulmonary artery. It improves patients' prognoses, but various late-phase extracardiac complications that manifest when patients reach adolescence have been recognized. These complications, pulmonary arteriovenous fistula and protein losing gastroenteropathy, for example, present significant challenges in the management of adults with Fontan circulation. Liver fibrosis is another possible late-phase complication and one of the most serious. Development of a neoplasm, usually a hepatocellular carcinoma, is sometimes reported. We encountered a young patient in whom Fontan circulation led to the development of a histologically unusual liver cancer that resembled the poorly differentiated hepatocellular carcinoma or the combined hepatocellular-cholangiocarcinoma with stem-cell features described in the latest WHO classification.