Origin of so-called mesothelioma of the atrioventricular node. An immunohistochemical study.

To determine the origin of a mesothelioma of the atrioventricular node, immunohistochemical studies that used various antibodies, including the antibody against mesothelial cells, were performed on a mesothelioma of the atrioventricular node in a case. The lining cells of the tubules that composed the tumor were negative when tested with anti-mesothelial cell antibodies. Carcinoembryonic antigen was negative, but the secretory component was positive. Serotonin and calcitonin were positive in a few cells. We concluded that a mesothelial origin was unlikely, and it was suggested that the tumor was of an entodermal origin.