Cardiac fibroma

Cardiac fibromafibromas, also known as cardiac fibromatosis, are benign congenital cardiac tumours that usually manifest in children. 

Epidemiology

Cardiac fibroma is a tumourfibromas are tumours that primarily affectsaffect children (most cases isare detected in infants or in utero) with a ratio of 4:1 compared with adults ⁵. They are the second most common benign primary cardiac tumour in children after cardiac rhabdomyoma and second most frequent fetal cardiac tumour ².

Clinical presentation

Cardiac fibromas are often associated with arrhythmias which can be a presenting feature. They can also cause hemodynamic compromise and congestive heart failure. These tumours also may be found incidentally in asymptomatic patients.  

Pathology

Microscopic appearance

Cardiac fibromas represent a collection of fibroblasts interspersed among large amounts of collagen (some authors believe that this tumour is a hamartoma rather than a neoplasm).

Macroscopic appearance

TheyThese tumours are well-defined, solitary, intramyocardial lesions with smooth margins and usually large, with a mean diameter of ~5 cm and may obliterate the ventricular cavity.

They almost always arise in the ventricles, most commonly in the ventricular septum and left the ventricular free wall, interventricular septum or right ventricular free wall (in descending order) ⁵.

Unlike many primary cardiac tumours, fibromas usually have no foci of cystic change, haemorrhage, or necrosis. Calcification is a common finding.

Associations

There is an increased prevalence of cardiac fibromas in Gorlin syndrome.

Radiographic features

CT

On CT, cardiac fibromas are homogeneous soft-tissue masses that are usually sharply marginated, but also can be infiltrative. Dystrophic calcification is commonseen in approximately 25% of cases ⁵. These lesions may enhance homogeneously or heterogeneously after administration of contrast. 

MRI

Due to their dense, fibrous nature, the tumours are usually homogeneous and hypointense on T2-weighted MR images and isointense relative to muscle on T1-weighted images. They are usually homogeneous unless there are calcifications, which may be seen as patchy hypointense foci within the lesion. Because of their avascularity, they often demonstrate little or no enhancement during the early phases after administration of intravenous contrast material enhancement; but may exhibit delayed hyperenhancement 7-10 minutes later since they have large extracellular space component.

Positron emission tomography (PET)

These lesions may exhibit homogeneous low-grade fluorodeoxyglucose uptake equivalent to that of the mediastinal blood pool. The lack of increased uptake may be reassuring against a diagnosis of aggressive malignancy. 

Differential diagnosis

• rhabdomyoma
  • also seen in young patients
• rhabdomyosarcoma
  • large and heterogeneous mass
  • invasive
• myxoma
  • intracavitary rather than intramural
• metastases 
  • known primary neoplasm
  • less likely in young patients
  • multifocal masses