Utility of cardiac imaging in diagnosis of atypical presentation of cardiac fibroma

Abstract

Primary cardiac tumours are relatively rare in the paediatric population, with benign tumours accounting for >90% of cases. Cardiac fibromas are rare primary tumours that typically reside in the ventricles. Symptoms are usually the result of blood outflow obstruction or disruption of the cardiac conduction system. They do not typically regress and usually require surgical intervention. In this case, we report a rare finding of a right atrial fibroma in an 18-month-old female who presented with lethargy and vomiting. Chest X-ray revealed an enlarged cardiac silhouette, and follow-up CT showed a 3.7×3.2×3.7 cm hypodense lesion in the right atrium. Cardiac MRI revealed the diagnosis, which was confirmed on pathology.

Background

Fibromas are the second most common cause of paediatric cardiac tumours. Fibromas typically arise from the ventricular septum, frequently invading the myocardium and presenting with congestive heart failure and arrhythmias. Cardiac fibromas typically do not regress and require surgical resection.¹ We present a case of atypical presentation of cardiac fibroma in an infant.

Case presentation

An 18-month-old female with no previous medical history presented to the emergency department with a 2-day history of respiratory distress, decreased appetite and vomiting. She was noted to have a large cardiac silhouette on chest X-ray and the echocardiogram revealed a homogeneous mass in the right atrium, compressing the superior vena cava (SVC) and a large pericardial effusion with tamponade physiology. Pericardiocentesis was immediately performed and 460 mL of haemorrhagic fluid was drained.

Investigations

Cardiac MRI was performed to characterise the mass. There was a 3×3.7×4.1 cm mass in the right atrium, which filled the right atrial appendage and extended upwards compressing the SVC. It was homogeneous, well circumscribed, isointense on T1-weighted and T2-weighted imaging, hypointense on first-pass perfusion and hyperintense on delayed enhancement imaging (figure 1). The features were suggestive of cardiac fibroma. As the mass appeared to be in close proximity to the right coronary artery, a cardiac CT was performed, which showed 3.7×3.2×3.7 cm mass in the anterior superior aspect of the right atrium filling the right atrial appendage without immediate hyperenhancement. There was a slight deviation of the proximal right coronary artery to the left from the large right atrial mass with loss of the fat adjacent to the proximal right coronary artery and moderate narrowing of the left mainstem bronchus (figure 2).

Figure 1.

(A) MRI cardiac with and without contrast revealing a well-demarcated, homogeneous, isointense 3.7×3.0×4.1 cm mass centred in the anterior wall of the heart with extension into the right atrium on T1-weighted turbo spin-echo (TSE) without fat saturation. (B) Isointense mass on T1-weighted TSE with fat saturation. (C) Isointense mass on T2-weighted TSE with fat saturation. (D) Mass showing significant delayed enhancement on 10 min myocardial delayed enhancement (MDE) imaging. (E) Mass demonstrating lack of contrast enhancement on first-pass perfusion. (F) Histology demonstrating extensive spindle cell proliferation with necrosis and inflammatory infiltrate, suggestive of cardiac fibroma (10×).

Figure 2.

(A) CT thorax with contrast revealing an enlarged cardiac silhouette, small bilateral pleural effusions, some left lower lobe atelectasis versus consolidation, and moderate narrowing of the left mainstem bronchus. (B) CT heart with contrast revealing a homogeneous mass measuring 3.7×3.2×3.7 cm in the anterior superior aspect of the right atrium with low density and no significant enhancement, suggestive of a cardiac fibroma. (C and D) 3D reconstructions showing a slight proximal right coronary artery deviation to the left due to the right atrial mass.

Treatment

A large fibrous firm mass was found partially adhered to the pericardium anteriorly, attached outside and inside the right atrium. The mass was also firmly attached to the atrioventricular groove of the right coronary artery. It was located approximately 1 mm away from the tricuspid valve, causing moderate leakage. The patient then underwent right atrial mass excision, primary patent foramen ovale closure and partial posterior De Vega type annuloplasty of the tricuspid valve. Histopathological analysis of the mass revealed variably cellular spindle cell proliferation with extensive infarction-type necrosis and areas of inflammatory infiltrate (figure 1). This was differentiated from inflammatory myofibroblastic tumour by the extensive inflammatory infiltrate and bland spindle histology.

Outcome and follow-up

The patient did well after surgery with no significant residual tumour and no arrhythmias were noted during the post-operative period. She was discharged home after a week.

Discussion

Primary cardiac tumours are relatively rare in the paediatric population with an incidence of estimated 0.027%, with benign tumours accounting for >90% of cases.^{2 3} Cardiac fibromas are the second most common type of primary cardiac tumour.⁴

Cardiac fibromas have unique pathological makeup. On histology, these fibromas are aggregates of fibroblasts interwoven with collagen. They are single masses that typically arise in the left ventricular free wall or the interventricular septum; atrial involvement is exceedingly rare.¹ Atrial involvement has been reported in a Down’s syndrome infant and adult patient, with an unknown prevalence.^{5 6} They are usually 1–10 cm in size and do not typically spontaneously regress.

Clinical presentation is dependent on tumour size and location. Complications include congestive heart failure, arrhythmias or sudden death. The mean age of diagnosis is 13 years.⁷ Gorlin syndrome—a rare genetic condition associated with basal cell carcinomas, odontogenic keratocysts, and skeletal anomalies—is seen in 3%–5% of adult patients diagnosed with cardiac fibroma.⁸

Cardiac MRI has recently become the gold standard for diagnosis and is the only imaging modality that can characterise the mass adequately. T1-weighted turbo spin-echo (TSE) with and without fat saturation, T2-weighted TSE with fat saturation, first-pass perfusion and delayed enhancement should be ordered to provide adequate characterisation of the mass. On cardiac MRI, cardiac fibromas have the following features: (1) well-demarcated, homogeneous masses that have a thin rim of myocardium; (2) heterogeneous appearance on T1-weighted and T2-weighted images; (3) hypointense on first-pass perfusion; (4) significant hyperenhancement with or without a hypoenhancing core on delayed enhancement imaging.⁹ In a recent meta-analysis of 78 cardiac tumour cases, MRI accurately diagnosed the tumour 97% of the time.⁹ A biopsy provides a definitive diagnosis. Our case highlights the importance of correct MRI sequencing, as we were able to correctly diagnose the patient with cardiac MRI even though the fibroma was in an atypical location.

Although MRI served as the crucial imaging modality for characterisation of the mass, CT provided valuable information regarding coronary anatomy and tumour blood supply, which was important for surgical planning. On CT imaging, cardiac fibromas appear as hypervascular, solitary masses with homogeneous or heterogeneous enhancement after contrast administration. Calcifications can be seen in up to 50% of cases, indicating poor blood supply.⁸ In our patient’s case, CT revealed a slight deviation of the proximal right coronary artery by the mass with effacement of adjacent fat and no vessel narrowing. Additionally, it is important to reduce the radiation burden with a low-dose protocol, especially in younger patients.⁷ This case highlights the importance of soft tissue characterisation by MRI and vasculature anatomy characterisation by CT to better enable physicians to accurately diagnose cardiac fibromas.

Spontaneous regression of cardiac fibromas has never been reported. Surgical mass excision is often required and is considered a desirable intervention for achieving the best prognosis. However, if resection is not feasible, medical management may be useful in the acute setting. This involves treating complications that arise due to mass effect and disruption of normal cardiac infrastructure. Various arrhythmias may occur as a consequence of cardiac fibromas and can lead to sudden cardiac death; these patients can be managed with antiarrhythmic therapy temporarily. Obstructive symptoms may also lead to congestive heart failure, necessitating medical management. Cardiac transplantation is another option for these patients.⁵

Our case highlights an atypical case of a cardiac fibroma, presenting in infancy and involving the right atrium. Few reports have been published to date on atrial cardiac fibromas, and thus this case underscores the importance of cardiac MRI and CT to adequately characterise this tumour and correctly diagnose this patient.

Learning points.

• Cardiac fibromas are typically found in the ventricles or ventricular septum. This case highlights an atypical presentation in the right atrium.

• Cardiac MRI has become the gold standard for diagnosing cardiac tumours. High accuracy in diagnosis can be achieved if the following sequences are done accurately: T1-weighted turbo spin- echo (TSE) with and without fat saturation, T2-weighted TSE with fat saturation, first-pass perfusion and delayed enhancement.

• Cardiac CT can provide valuable information regarding coronary anatomy. In our case, the fibroma was found to be receiving blood supply from the right coronary artery which was important for surgical planning.

• Cardiac fibromas can lead to several complications including arrhythmias, congestive heart failure and haemorrhagic pericardial effusions, often necessitating surgical intervention.