Mesothelioma of the AV node

Cystic tumor of the atrioventricular node: a review of the literature

Primary cardiac tumors are uncommon clinical entities with an incidence of 0.0017% to 0.03% of all autopsies. Cystic tumor of the atrioventricular (AV) node, also known as mesothelioma of the AV node, is a benign congenital tumor that is located in the triangle of Koch in the AV nodal region of the atrial septum of the heart. It comprises of 2.7% of cardiac tumors and is the most common primary cardiac tumor causing sudden death. We herein review the etiology, presentation, differential diagnosis, diagnosis, management, surgical approaches and outcomes of this rare tumor.

Tumors associated with sudden infant and childhood death

Tumors are rare causes of sudden death in infancy and early childhood. The goals of this study were to determine the types and frequency of the tumors associated with sudden death occurring in cases between birth and age 3 years. The San Diego Sudden Infant Death Syndrome/sudden unexplained death in childhood (SUDC) Research Project database and the literature were reviewed retrospectively. Sixty-eight cases, with the most (84%) affecting the heart and brain, were identified. Tumors are a rare but significant cause of sudden death in infancy and early childhood, and their diagnosis may have significant genetic implications for planning future pregnancies. The diagnosis of these lesions can be established only after thorough postmortem examination.

Primary pediatric cardiac tumors: a 17 year experience

We reviewed 22 cases of primary pediatric cardiac tumors followed at our institution from January 1981 through November 1997, analyzing them by subtype, age and manner of presentation, location, associated findings, interventions, and clinical course. Rhabdomyomas were the most common (11), followed by intrapericardial teratomas (2), myxomas (1), fibromas (1), hemangiomas (1), mesotheliomas (1), and rhabdomyosarcomas (1), with 4 undetermined tumors. The majority (77%) of tumors were diagnosed before the age of one year, including six prenatally. The most common presentations were murmurs (5), arrhythmias (5), and abnormal screening fetal ultrasound examinations (4). Tumors were located most frequently in the right ventricle (13) and left ventricle (7), with multiple tumors being present in 10 cases. Eight patients (36%) had associated arrhythmias or conduction abnormalities, and of the 11 patients with rhabdomyomas, tuberous sclerosis was diagnosed in 8. Eight patients underwent cardiac catheterization, including two for electrophysiologic study with radiofrequency ablation, and seven patients had complete or partial tumor resection. The follow-up period ranged from 2 months to 15 years, and there were 3 tumor-related deaths. Therefore, despite the benign histology of most primary pediatric cardiac tumors, there may be significant associated morbidity and occasional mortality. As echocardiographic techniques such as fetal ultrasonography have continued to improve, however, these cardiac tumors have increasingly been detected early before significant symptoms develop.

Histological evidence for cell proliferation activity in cystic tumor (endodermal heterotopia) of the atrioventricular node

Cystic tumor (endodermal heterotopia) of the atrioventricular (AV) node in a 95-year-old female is described. Electrocardiograms showed complete AV blockage with a narrow QRS morphology resulting from the long-standing first degree of AV blockage since age 61. A cardiac pacemaker was implanted at age 83. The patient died of pneumonia at age 95. Autopsy demonstrated a normal heart weight (320 g), normal coronary artery and normal myocardium. Histological examination of the conduction system revealed a marked fibrotic sinoatrial (SA) node and a cystic lesion in the lower right atrium, including the approaches to the AV node. The bundle of His and its branches were completely intact. Cellular nests and cystically dilated tubules were scattered within a loose tissue stroma, which measured 18 x 12 x 5 mm. There were several mitotic figures among the tubules, as well as nuclear fragments similar to apoptotic bodies and exfoliation of the tumor cells. Immunohistochemical studies demonstrated a positive reaction for epithelial membrane antigen, carcinoembryonic antigen, CA19-9, cytokeratin and secretory component in the tubular cells, and a negative reaction for thrombomodulin. Endocrine cells among the tubules were positive only for calcitonin and serotonin. Ultrastructurally, sparse microvilli and desmosome-like structures between the tumor cells were observed. These findings support that this lesion originates from the endoderm. Moreover, it is likely that progression in the degree of AV block may be explained by the cell proliferation activity of the tumor.

Primary cardiac tumors causing sudden death: a review of the literature

Sudden unexpected death accounts for 200,000-400,000 deaths each year in the United States. Although the vast majority of these fatalities are related to atherosclerotic heart disease, a small percentage (approximately 0.0025%) stem from primary cardiac neoplasms. There have been 120 cases of sudden death attributed to primary cardiac tumors in the (published) literature. Although 103 of these lesions were histologically benign (86%), their intracardiac locations precipitated conductive and hemodynamic abnormalities that resulted in sudden death. These tumors are usually easily recognized at necropsy. The most common intracardiac lesion causing sudden death, endodermal heterotopia of the atrioventricular (AV) node, however, may not be discovered unless the AV node is microscopically examined. Owing to the rarity of these neoplasms, a brief review of their salient gross and microscopic features is in order.

Background incidence of mesothelioma: animal and human evidence

Evidence is presented showing that mesotheliomas can have causes other than exposure to asbestos dust, in both experimental animals and humans. In experimental animals, for example, results from two major experimental laboratories suggest that at least 10% may be taken for background incidence, whereas a third laboratory suggests that the experimental group must have a rate exceeding 30% "Background" also includes mesotheliomas found in association with nonfibrous and fibrous nonasbestiform agents. Mesotheliomas in humans can be broadly classified in a manner similar to those of experimental animals: (1) spontaneously occurring, (2) those with a latent period less than 10 years, (3) childhood mesotheliomas, (4) familial cases, (5) cases before the 20th century, (6) mineralogically negative mesotheliomas, and (7) mesotheliomas caused by nonasbestiform agents. The importance of the acceptance of these "background" cases lies in the fact that a basis is provided for the study of the incidence of disease associated with various types of asbestos.

Mesothelioma of childhood

Malignant mesothelioma (MM) of childhood is a rare but important neoplasm. Eighty children with a previous diagnosis of MM were identified. Four of the 80 children had exposure to known risk factors (two had history of exposure to asbestos, one had received radiation therapy, and one had been exposed in utero to isoniazid). Tissue slides were available for independent and joint review by a panel of three pathologists in 22 of the cases. Ten were accepted as MM, nine were reclassified as other malignancies, and three were considered tumors of uncertain nature. Six of the ten children with MM were boys, and four were girls. Eight had pleural tumors, and two had peritoneal tumors. Four died at 7, 8, 18, and 48 months after diagnosis; three remained alive at 19, 20, and 59 months; and three had no follow-up. This review suggests that MM of childhood is a valid entity with a grave prognosis. The tissue diagnosis is difficult and is best made by a panel of pathologists. The available evidence does not support a causal relationship between MM and asbestos, radiation, or isoniazid.