A 17-year-old patient presented with a recurrent right atrioventricular (AV) groove vascular tumor. The tumor was resected en bloc, including the AV groove extending into the right ventricle (RV) and tricuspid valve. The AV groove and tricuspid valve required extensive reconstruction. The histopathologic features were that of an arteriovenous malformation with a proliferative small vessel component--an extremely rare type of cardiovascular anomaly.