Congenital polycystic tumor of the atrioventricular node: possible familial occurrence and critical review of reported cases with special emphasis on histogenesis

A Transplantable Epithelial Atrio-Caval Tumour in NZR/Gd Rats

A permanently transplantable tumour line, ACT-1, has been established from one of the unusual epithelial atrio-caval tumours characteristic of NZR/Gd rats. Data are given on the adaptation of the tumour to serial transplantation, its growth rate, and histologic structure.

Cystic tumor of the atrioventricular node: an unexpected finding in an explanted heart

SUMMARY

We report herein a unique case of cystic tumor of atrioventricular (AV) node (CTAVN), which, to our knowledge, is the first of its kind diagnosed in an explanted heart specimen and only the fourth diagnosed antemortem. Often, this rare tumor can only be diagnosed by careful gross examination and adequate sampling of AV node region. It is an important differential diagnosis in young patients with syncopal attacks and varying degrees of heart blocks.

CONTEXT

CTAVN is a rare, benign tumor. Most cases have been reported in young females (mean age, 38 years). Patients typically present with conduction abnormalities including complete heart block leading to sudden cardiac death. Most cases have been identified at autopsy; no cases to our knowledge have been reported in an explanted heart.

DESIGN

A 19 year-old female presented to the cardiac transplant clinic for evaluation of severe congestive heart failure felt to be secondary to postpartum cardiomyopathy. The patient's history was significant for congenital heart block requiring placement of a permanent pacemaker at 12 years of age. At the time of this presentation, electrocardiogram revealed second-degree AV block, and two-dimensional echocardiogram showed lipomatous hypertrophy of the interatrial septum. Seven months later, orthotopic cardiac transplantation was performed.

RESULTS

On gross examination, the explanted heart weighed 500 g and had biventricular dilatation. Histologic sections of left and right ventricle revealed myocyte hypertrophy and interstitial fibrosis consistent with dilated cardiomyopathy. Sections from the AV node showed a lesion with morphological features of CTAVN. It was composed of cysts of varying sizes lined by transitional, cuboidal and squamous epithelium. Some cysts were filled with proteinaceous debris that were periodic acid Schiff-positive and diastase resistant.

CONCLUSIONS

CTAVN occurs exclusively in the area of the AV node, tricuspid valve, and inferior atrial septum. These lesions are now believed to be endodermal in origin, although mesothelial origin was earlier proposed. We report herein a case of CTAVN, the first of its kind diagnosed in an explanted heart specimen and only the fourth diagnosed antemortem.

Sudden Cardiac Death in a Young Woman

Atrioventricular (AV) node tumor is a very rare lesion of the cardiac conduction system. Clinically, it is associated with complete AV block and sudden cardiac death, often in apparently healthy young people. We report a case of a 24-year-old woman who developed ventricular fibrillation during sexual intercourse and died before admittance to the hospital. The woman had a medical history of depression and was treated with citalopram.At first, no macroscopic or microscopic pathologic changes were found. Toxicologic analysis showed a toxic level of citalopram in the blood. Further microscopic examination of the cardiac conduction system disclosed a tumor of the AV node. Immunohistochemical staining confirmed endodermal origin in accordance with the latest hypothesis of the pathogenesis of this tumor. It was concluded that this young woman died of cardiac arrhythmia due to the AV tumor and not from citalopram intoxication, as first suspected. This case emphasizes the importance of a microscopic examination of the cardiac conduction system in cases of sudden unexpected death, even in cases with a plausible cause and manner of death at first glance.

Successful Excision of a Cystic Tumor of the Atrioventricular Nodal Region

Cystic tumor of the atrioventricular nodal region is a rare cardiac primary tumor that can cause heart blockage and sudden death. Antemortem diagnosis and successful excision of the atrioventricular nodal region are extremely rare. A 45-year-old woman who presented with palpitations is reported. Electrocardiography revealed first-degree atrioventricular block. Echocardiography, computed tomography, and magnetic resonance imaging scans revealed a cystic mass attached to the interatrial septum. Complete surgical excision of the mass was achieved, although placement of a permanent pacemaker was required for complete heart blockage. Histopathological examination revealed the mass to be a cystic tumor of the atrioventricular nodal region. A 5-year follow-up has revealed no sign of recurrence.

Endodermal heterotopia of the atrioventricular node associated with transposition of the great arteries

A 13-year-old girl with surgically corrected complete transposition of the great arteries died suddenly while walking to school. Postmortem examination revealed endodermal heterotopia of the atrioventricular node, a condition not previously associated with transposition of the great arteries. New immunohistochemical observations are described, and the embryogenesis of the condition and its association with complete transposition are discussed.

Cystic tumor of the atrioventricular nodal region

We report a case of a 66-year-old female who presented exertional dyspnea and palpitation. Echocardiography, transesophageal echocardiography and computed tomography showed a right atrial cystic mass attached to the interatrial septum. The patient underwent successful excision of the mass. The histopathological findings confirmed the lesion as a cystic tumor of the atrioventricular nodal region. This is the third known case of this condition diagnosed antemortem and treated successfully with surgical excision.

Cystic tumour of the atrioventricular nodal region: report of a case successfully treated with surgery

A case is reported of a 59 year old woman who presented with palpitations. Electrocardiographic studies revealed atrial fibrillation and atrioventricular block. Echocardiography and magnetic resonance imaging showed a right atrial cystic mass attached to the interatrial septum. The patient underwent surgical excision of the mass. Histopathological findings were of a cystic tumour of the atrioventricular nodal region. This is the second report of this condition diagnosed antemortem and treated successfully with surgical excision.

An unusual site for the AV node tumor: report of two cases

Atrioventricular (AV) node tumors are very uncommon primary cardiac tumors located exclusively in the AV nodal region. The nomenclature has been diverse according to different histogenetic theories proposed since the first description in 1911. Histochemical, ultrastructural, and immunohistochemical studies have demonstrated its endodermal origin. Patients with these tumors can develop complete heart block or sudden death, but the tumor can also be an incidental finding at autopsy. We present two accidental deaths cases in which multiple foci of atrioventricular node tumor (Case 1) and an isolated cyst (Case 2) were observed in the atrial septum, sparing the conduction system.

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.

Bovine myocardial epithelial inclusions

Light microscopic, histochemical, immunohistochemical, and ultrastructural methods were used to examine myocardial epithelial masses in the hearts of ten cattle. The tissues consisted of paraffin-embedded or formalin-fixed samples from eight hearts that were being inspected in slaughter houses and from two hearts from calves that died of septicemia. The ages of the cattle ranged from 4 days to 12 years; the breeds were unspecified for all but one Hereford female and the two Holstein calves; and there were three males, four females, and three steers. The masses in these cases were compared with similar appearing lesions found in other animal species. The lesions in the bovine hearts were single to multiple, well circumscribed, found in the left ventricle wall, and composed of squamous to cuboidal epithelial cells that formed tubular, ductular, and acinar structures with lumens that were void or filled with amorphous protein globules. Electron microscopic examination revealed epithelial cells that had sparse apical microvilli, tight apical intercellular junctions, perinuclear bundles of filaments, and rare cilia. Almost half of the bovine epithelial masses (4/9) had occasional diastase-resistant periodic acid-Schiff-positive granules in their cytoplasm, and few had hyaluronidase-resistant alcian blue-positive granules (2/9) or colloidal iron-positive granules (1/9). All myocardial masses had abundant collagen surrounding the tubular and acinar structures, and 2/9 had elastin fibers as well. None of the myocardial masses had Churukian-Schenk or Fontana Masson's silver staining granules in epithelial cells. Immunohistochemically, all bovine myocardial tumors stained positively for cytokeratin (8/8), and occasional masses stained positively for vimentin (3/8) or carcinoembryonic antigen (3/8). None of the masses stained positively for desmin. The myocardial epithelial tumors most likely represent endodermal rests of tissue misplaced during organogenesis.

Cardiac myxoma with a cytokeratin-immunoreactive glandular component

This study documents the expression of cytokeratin intermediate filaments (IFs) in a surgically excised glandular atrial myxoma. The glandular structures showed also positivity for carcinoembryonic antigen. Typical isolated or cordlike myxoma cells contained vimentin IFs. Positivity for von Willebrand factor was detected in cells lining deep invaginations of surface papillae and vascular channels. Bundles of smooth muscle cells and myofibroblasts scattered throughout the myxoid matrix synthesized the isoform of alpha-actin specific for smooth muscle.

Mesothelioma of the atrioventricular node and congenital complete heart block

Congenital complete heart block (CCHB) has heterogeneous etiologies. It may occur as an isolated entity with no associated congenital cardiac malformations and is difficult to diagnose even with modern technology. Mesothelioma of the atrioventricular (AV) node is a benign tumor that causes CCHB. The occurrence of this tumor is rare, and a definitive diagnosis of the entity is made only at autopsy. The conduction disturbance caused by the mesothelioma is potentially treatable and should be considered in the differential diagnosis of CCHB. We present a case report of a 38-year-old female with CCHB caused by such a tumor. Clinical diagnosis and treatment of CCHB are reviewed.

Synovial sarcoma of the heart arising from a so-called mesothelioma of the atrio-ventricular node

A primary tumour of the right atrium with morphological, ultrastructural and immunohistochemical features of a synovial sarcoma is described. This appeared to have arisen from a benign so-called mesothelioma of the atrio-ventricular node and had metastasized to the lungs. The histogenesis and relationship of these two tumours are discussed.

Congenital polycystic tumor of the atrioventricular node (endodermal heterotopia, mesothelioma): a histogenetic appraisal with evidence for its endodermal origin

The small, variously designated, primary atrioventricular node tumor has been considered to be of endothelial, endodermal, or mesothelial origin. To identify its derivation, we studied seven tumors using silver staining and immunocytochemical labeling with a variety of antibodies. Cytoplasmic argyrophil granules but not argentaffin granules were found in isolated cells among the more numerous tubule-lining cells in four tumors. Serotonin and calcitonin were demonstrable in seven and six tumors, respectively, in a similar distribution to that of the argyrophil cells. A positive reaction of different distribution from that of the argyrophil cells was noted in a varying number of tubule-lining cells for carcinoembryonic antigen, epithelial membrane antigen, and blood group antigen in seven, four, and seven tumors, respectively. No activity was noted in the tumor cells for factor VIII-related antigen or a number of peptides. An endodermal rather than mesothelial or epithelial origin for the tumor is substantiated by the presence of neuroendocrine cells in the midst of the more numerous carcinoembryonic-antigen-positive lining cells of the tumor tubules.

Congenital endodermal heterotopia of the atrioventricular node: evidence for the endodermal origin of so-called mesotheliomas of the atrioventricular node

A case of so-called mesothelioma of the atrioventricular node is presented. Controversy exists as to whether this lesion is of mesodermal or endodermal origin. The light and electron microscopic morphologic characteristics in this case were identical to those reported previously. The glandular component produced mucin that resisted digestion with both hyaluronidase and diastase; this staining pattern is characteristic of endodermal rather than of mesodermal tissue. Immunohistochemical methods demonstrated abundant carcinoembryonic antigen (CEA) in the cytoplasm of the cells composing the lesion. The presence of CEA strongly argues for an endodermal origin, since this antigen characterizes tissue derived from endoderm and is generally absent from mesoderm. The lesion probably represents endodermal foregut tissue that is displaced during embryogenesis. As such, it is not a true neoplasm. It is proposed that this lesion be designated "congenital endodermal heterotopia of the atrioventricular node."

Teratoma of the heart. A case report and review of the literature

The clinical manifestations and pathological features of an extremely rare cardiac tumour, a mature (benign) teratoma, in a 6 year-old girl are described. These are compared with those reported in the literature.