Cardiac Path Online

Pathology of Mesothelioma of the Atrioventricular Node (Cystic Tumour of Atrioventricular Node)

" Smallest Human Tumour that can cause sudden death"

Dr Sampurna Roy MD




These are multicystic tumours of the atrioventricular node which originate during embryogenesis of heart.

Their histogenesis is debatable and various suggestions are:

1.  Derived from the invaginations of epicardial  mesothelium within atrioventricular canal.

2.  Derived from displaced endodermal foregut tissue (suggested from positive immunostaining for CEA and keratin).

Thus pathogenetically, these lesions are similar to bronchogenic cysts.

Clinical presentation :  These may occur at any age and partial or complete atrioventricular heart block is the dominant feature. 

Often sudden death may be the first sign of this tumor.

Almost all published cases were diagnosed after  postmortem examination.

The tumour may completely replace the atrioventricular node which may lead to intra-atrial conduction defect,  paroxysmal atrial arrhythmia and spontaneous intermittent  pre-excitation (through multiple left-sided accessory pathways).

Gross features:  There is thickening of the atrial septum  with or without elevated nodules in the region of atrioventricular node.

Microscopic features:  Polycystic lesion may replace the atrioventricular node.

It is composed of cysts, ducts and solid nests of cells.

Cavities are lined by single or multilayered cuboidal cells.

The cells are PAS (diastase resistant) and alcian blue positive.

Some cell nests resemble squamous or transitional epithelium.

Image of Nodule of Atrioventricular Node (

Practical point to remember:

Cystic tumour of the A-V node, is the most common primary cardiac tumour causing  sudden death.

Macroscopic findings of this lesion may not be prominent and can be easily missed.

It has been recommended to take a routine section of the conducting system, including the AV node, in all cases of sudden death.

Cardiac Pathology Online


http://www. HeartIndex. htm

Further reading:

Benign cardiac tumours associated with sudden death

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

'So-called mesothelioma' of the atrioventricular node- immunohistochemical study.

So-called mesothelioma of the atrioventricular node.

Heart block, sudden death, and atrioventricular node mesothelioma.

Ultrastructure of the mesothelioma of the atrioventricular node.

Smallest  tumour which causes sudden death- JAMA 1965 ; 194: 674-675




Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)









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