Intracardiac teratoma in a child simulating an atrioventricular nodal tumor.

Intracardiac teratoma is an extremely rare pediatric neoplasm. We studied the case of a 6-year-old girl with a right intraventricular cardiac mass. The tumor consisted of clusters of monotonous round epithelial cells scattered in a dense fibrotic stroma and was thought to represent an atrioventricular nodal tumor. Three years later the tumor recurred, with multiple mature elements derived from all three germ layers, and was diagnosed as mature cystic teratoma. Still present, however, were multiple areas that were histologically similar to the earlier lesion. Immunostaining revealed strong positivity for insulin, glucagon, somatostatin, and chromogranin consistent with overgrown pancreatic islets of Langerhans within a mature teratoma.