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Pathology of Cardiac Rhabdomyoma
Cardiac rhabdomyoma is the most common benign congenital cardiac tumour.
It is thought that the tumour is a hamartoma rather than a true neoplasm.
This is the most common tumour in infants and children.
Cardiac rhabdomyomas are prenatal echocardiographic markers for tuberous sclerosis complex (TSC). Tuberous sclerosis complex TSC is caused by mutations in the genes TSC1 and TSC2.
Cardiac rhabdomyoma occurs in more than 50% of patients with tuberous sclerosis.
Site: Any chamber of the heart may be affected. The left ventricle is the most frequently involved site.
Clinical presentation: Clinical profile varies from still-birth to intrauterine myocardial infarct (due to coronary artery compression).
Cardiac rhabdomyoma is frequently multiple and asymptomatic, but the tumour may cause cardiomegaly, heart failure by causing outflow obstruction, arrhythmias, thromboembolic disease or sudden unexpected death.
Gross features: The tumour may present as a single or multiple , non-capsulated soft lesion which can be easily distinguished from the surrounding myocardium.
Diffuse rhabdomyoma are extremely rare.
Large tumours may show intracavitary extension with almost obliteration of the cavity (Differential diagnosis: may be confused with cardiac myxoma).
Histologically the tumour is composed of 'spider cells'.
Spider cells are large swollen myocytes with clear cytoplasm and centrally placed cytoplasmic mass and nucleus, connected with the periphery of the cell by strands of cytoplasm.
The spider cells are surrounded by normal cardiac myocytes.
Fate of the tumour:
Cardiac rhabdomyoma decreases in size with age.
Echocardiographic evaluation has confirmed the spontaneous regression with eventual disappearance of cardiac rhabdomyoma.
Hence, cardiac surgery should be delayed to see whether or not the tumour would regress.
Such biologic behavior supports the concept that cardiac rhabdomyomas are hamartoma rather than a true neoplasm.
- Glycogen storage disease (shape of the cardiomyocytes are well preserved).
- Purkinje cell tumour (Foamy myocardial transformation)
- Hamartoma (no cytoplasmic vacuolation).
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