Abstract
We present the case of a 64-year-old man who was incidentally found to have a left atrial mass in the vicinity of the left atrial appendage. Despite adequate anticoagulation for suspected thrombus for 6 months, the appearances of the mass remained unchanged. Surgical resection was recommended to reduce the risk of embolisation and to establish a histopathological diagnosis. Despite our initial suspicions of this being a myxoma the mass was ultimately confirmed to represent a rare papillary fibroelastoma occurring on the endocardial surface of the left atrium. The current report details the multimodality imaging of this phenomenon along with the diagnostic dilemma this unusual left atrial mass initially posed.
Introduction
Left atrial masses pose diagnostic challenges due to their diverse aetiologies and overlapping clinical and imaging features [1, 2]. The task confronting clinicians faced with the finding of a left atrial mass includes the formulation of a differential diagnosis using available clinical data and the subsequent utilization of multimodal imaging in order to modify this differential, quantitate patient risk, and direct treatment.
Presenting history
A 64-year-old man with dyslipidaemia but no other co-morbidities presented with atypical chest pain to his local hospital. Subsequent coronary computed tomographic angiography (CTA) showed no significant coronary disease. Note was made however of a large 30 mm heterogeneous mass at the orifice of the left atrial appendage (Fig. 1).
Coronary computed tomography. Panel A: Axial slice of the left atrium with a low attenuating mass seen lodged within the orifice of the left atrial appendage. Panels B and C: Oblique coronal and sagittal views showing the mass (arrow) within the left atrial appendage. This mass did not extend to the tip of the left atrial appendage and was irregular. It was therefore thought unlikely to be a thrombus. Panel D: Endoscopic view of the left atrium. The mass can be seen (arrow) extending into the left atrial cavity between the left superior and inferior pulmonary veins and attached by a stalk at the mouth of the left atrial appendage (arrow). LA: left atrium; RA: right atrium; LV: left ventricle; RV: right ventricle; Ao: aorta; AoV: aortic valve; MV: mitral valve; LSPV: left superior pulmonary vein; LIPV: left inferior pulmonary vein
Citation: Imaging 2024; 10.1556/1647.2024.00237
Diagnosis, investigations and initial management
Although the patient was in sinus rhythm he was promptly commenced on a direct oral anticoagulant for a suspected left atrial thrombus. Subsequent transthoracic echocardiography showed normal biventricular systolic function, normal left atrial size and no heart valve abnormalities. Given that cardiac magnetic resonance imaging was not possible owing to a long-standing foreign body in the patient's orbit, he underwent a positron emission tomography-computed tomography scan (PET-CT scan). This showed no cardiac or extracardiac uptake. Following 6 months of anticoagulation a further coronary CTA was performed that showed no change in the size of the mass despite 6 months of anticoagulation. The patient was subsequently referred to our centre for a second opinion and further management.
Differential diagnosis
Upon review, we felt the mass to be atypical for thrombus owing to their being contrast present on the CT scan at the left atrial appendage apex. There was also a small stalk identified and a potential attachment point just proximal to the orifice of the left atrial appendage. These suspicions were supported by both the transoesophageal echocardiogram (TOE) findings (Fig. 2), and a lack of response to anticoagulant therapy. We concluded, that the likely diagnosis was of a primary cardiac tumour, most likely an atypical myxoma, but that a papillary fibroelastoma and lipoma were also within the differentials. Secondary metastases were felt to be unlikely in the context of the patient being constitutionally well and with no significant findings being detected on metabolic imaging or thoracic imaging.
Transoesophageal echocardiogram. Panels A–C: High oesophageal views showing a large left atrial mass (arrow) lodged within the left atrial appendage (*). The mass was cystic and appeared to be attached by a stalk at the mouth of the left atrial appendage. The mass measured 30 × 17 mm on the 90° view (Panel B) and 26 × 18 mm on the 126° view (Panel C). LA: left atrium
Citation: Imaging 2024; 10.1556/1647.2024.00237
Management and final diagnosis
The case was thereafter discussed at a specialist heart team meeting where surgical resection was recommended for suspected unusual left atrial myxoma. This was performed without complication with the macroscopic appearance being consistent with a myxoma (Fig. 3). Subsequent histopathological examination confirmed the mass as being a papillary fibroelastoma rather than a myxoma with fibrous characteristics, a myxoid/eosinophilic matrix lined by endothelial cells, and an avascular core containing elastin fibres, typical for a fibroelastoma (Fig. 3). At six months the patient was well with no imaging evidence of recurrence.
Surgical macroscopic appearance. Panel A: Left atrial mass – smooth mushroom like appearance, gelatinous in nature with an irregular surface and a stalk (arrow).
Histopathological slide. Panel B: The mass was described as gelatinous in origin with fibrous characteristics and a myxoid/eosinophilic matrix lined by endothelial cells. The core was vascular (white spaces) and contained elastin fibres (pink) typical for a fibroelastoma
Citation: Imaging 2024; 10.1556/1647.2024.00237
Discussion
Cardiac tumours are rare with secondary metastatic spread having a necropsy incidence of 1% and primary cardiac tumours an incidence of 0.02%. Given this difference, when atypical cardiac masses are detected it is prudent that firstly metastatic spread is excluded. When considering the possibility of primary cardiac tumours, myxomas account for 50% of all cases with the commonest site being interatrial septal surface of the left atrium (75–85%) followed by the right atrium (10–15%) and the ventricles and valvular surfaces in 5%. Fibroelastomas on the other hand are normally found in isolation on the cardiac valves, most commonly on the ventricular side of the aortic valve and atrial side of the mitral valve [1, 2]. It is important to recognise however that they can occur on any non-valvular endocardial surface. Although their usual mean size is 9 mm, they can grow to sizes of up to 70 mm [3], where they share the same imaging and macroscopic characteristics as myxomas. Importantly they carry a similar risk of thromboembolism and prompt surgical excision is usually recommended.
Conclusion
In the current case we firstly show the multimodality imaging appearances of an unusual left atrial mass that initially mimicked the appearance of a large left atrial thrombus. Secondly, we show the diagnostic pathway used to reach a diagnosis of what was ultimately established to be a large papillary fibroelastoma arising from the left atrial wall that had become lodged within the left atrial appendage.
Author's contribution
Can Zhou conceptualised the manuscript and was responsible for the manuscript preparation. Paolo Bosco was responsible for the surgical photographs and provided critical revisions to the manuscript. Ramnith Perera provided histopathology input to the manuscript. Natalie Montarello, Ronak Rajani and Camelia Demetrescu aided in the drafting of the manuscript and provided critical input into the manuscript.
Conflict of interest
None.
Funding sources
There were no funding sources for the current manuscript.
Ethical statement
Not applicable.
References
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Bussani R, Castrichini M, Restivo L, Fabris E, Porcari A, Ferro F, et al.: Cardiac tumors: diagnosis, prognosis, and treatment. Curr Cardiol Rep 2020; 22(12): 169.
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Yandrapalli S, Mehta B, Mondal P, Gupta T, Khattar P, Fallon J, et al.: Cardiac papillary fibroelastoma: the need for a timely diagnosis. World J Clin Cases 2017; 5(1): 9–13.
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Cardy C, Riddle N, Dunning J, Chen A: Giant tricuspid valve fibroelastoma incidentally diagnosed during routine stress testing. JACC Case Rep 2019; 1(4): 564–568.
