A patient with complete atrioventricular block and an implanted perman
ent pacemaker died of colon cancer at the age of 64 years. At autopsy,
a cardiac tumor in the region of the atrioventricular node (mesotheli
oma of the atrioventricular node) was found. The origin of this type o
f tumor is controversial. Histochemical findings suggested that the tu
mor in this case was of endodermal origin.