Cystic Tumor of the Atrioventricular Node

**Semantic type:** Neoplastic Process

**Definition:** A multicystic tumor arising in the inferior interatrial septum in the region of the atrioventricular node. The vast majority of patients present with complete heart block and a minority with partial heart block. Sudden death is reported in approximately 10% of the cases. It is a morphologically benign tumor composed of cuboidal, transitional, or squamoid cells. The cells may also show sebaceous differentiation and originate from the endoderm.

**Synonyms:** - Benign Mesothelioma of Mahaim - Cystic Tumor of Atrioventricular Node - Cystic tumor of atrio-ventricular node - Endodermal Rest - Intracardiac Endodermal Heterotopia - Mesothelioma of Atrioventricular Node - Tawarian Node