Case presentation
A previously healthy 44 years-old female patient presented to our Hospital from an outpatient cardiology clinic with an echocardiographic finding of a floating mass within the left atrium.
She was symptomatic for a few months for asthenia, dyspnoea and dizziness She denied lypothymia or syncope and any history of drug/alcohol abuse or recent travels.
Her family history was negative for cardiovascular/neoplastic diseases.
The patient was in good clinical conditions, NYHA class I and CCS 0. Cardiac auscultation revealed a classical diastolic “tumour blop”, not accompanied by any other significant murmur.
An urgent transthoracic echocardiogram with 3D digital reconstruction of the images was performed and confirmed the primary diagnosis (Fig. 1). The mass originated from ovalis fossa on the left side of the interatrial septum.
Maximum diameter was 3.5 x 3 cm. The mass had a lobulated and polypoid architecture and a narrow implantation stalk, appearing unstable, and prolapsed across the orifice of the mitral valve during diastole.
To complete the diagnostic framework, a cardiac, lung and brain CT scan (Fig 2) were performed, without any pathological finding and recent cardio-embolic events were also excluded.
The patient was then scheduled for surgery.
The operation was performed trough a left atriotomy. The tumour presented as a pale pink, grape-like, semi-transparent mass. It had a particularly gelatinous and friable consistency with a high risk of fragmentation during surgical manipulation. Due to these atypical characteristics, we suspected the malignant nature of the neoplasm.
In order to perform a cautious removal of the mass, we started resecting it 2 mm from the implant base using a #11 scalpel blade to reduce the risk of tumour fragmentation.
The next step was to perform a radical full-thickness resection of the implant base, located on the atrial septum, leaving a safety margin of 5 millimetres. Repeated and extended washing of the left chambers of the heart followed to reduce the risk of remaining tumour fragments embolization.
The redundant interatrial septum, though largely resected, was closed by a direct suture.
No complications occurred in the postoperative period, and the patient was discharged on the sixth post-operative day to a rehabilitation facility.
At gross examination, surgical specimens included: a lesion with dimensions of 3,5 x 3 cm pedunculated, translucid and with a villous surface, focally covered by fibrinous exudate; a 1,5 cm implantation stalk and a fragment of interatrial septum.
Histological analysis showed that the lesion was made up of myxoid matrix containing thin vessels and scattered stellate cells without mitotic activity and cytologic atypias. Interestingly, the fibrinous layer focally covering the lesion contained few dense aggregates consisting of large, blastic lymphoid cells, with clear-cut atypical features (Fig.3).
At immunohistochemical staining, the stellate cells embedded in the myxoid matrix were positive for CD34, and negative for cytokeratins AE1/AE3, CD31 and CD45/LCA, and with a very low (< 2%) Ki67 proliferation rate. Such findings were consistent with cardiac myxoma.
Further immunohistochemical evaluation showed a B-cell phenotype (positive for CD20, PAX5, CD79A) of the atypical, blastic lymphoid cells, along with partial positivity for BCL6, IRF4, BCL2, CD30 and C-MYC (< 40% of cells), negativity for CD10, CD5, CD15, ALKc and HHV8, and a very high Ki67 proliferation index (> 80%). In situ hybridization for Epstein-Barr virus (EBV/EBER) was diffusely positive (Fig. 3).
Histologic features and incidental finding were all consistent with an EBV-positive fibrin-associated large B-cell lymphoma, arising within a cardiac myxoma.
The implantation stalk was focally involved by myxoma, but free of lymphoma, suggesting a complete resection of the lesion.
Total body CT scan and 18-FDG Positron Emission Tomography excluded distant metastases. Oncologic consultation did not give any indication for adjuvant chemotherapy or radiotherapy.