Case description
An 85-year-old man presented to the emergency department due to acute onset of fatigue and weakness. His emergent electrocardiogram (ECG) showed serious atrioventricular block with a heart rate of 43 bpm (Figure 1A). After hospitalization, atrioventricular block of different degree was recorded, and intermittent bradycardia occurred frequently. Intriguingly, his transthoracic echocardiogram (TTE) revealed a pedunculated mass of about 34 × 34 mm in the right ventricle (Figure 1B, arrow) attached to the right atrial wall, and the mass oscillated between the right ventricle and right atrium with the cardiac cycle, which could block the tricuspid orifice during the diastolic phase and was suggestive of atrial myxoma. Enhanced computed tomography (CT) scan of the whole body did not reveal lymphadenectasis or other suspicious masses, except a mass with clear boundaries in the right ventricle (Figure 1C, arrow). However,because of previous history of hip arthroplasty, he cannot receive the cardiac MRI which could indicate more characterisation of this cardiac mass.
The patient underwent open heart surgery because of the clinical suspicion of myxoma. After surgical removal of the tumor, serious atrioventricular block was diminished, but ECG recorded first-degree atrioventricular block on rare occasions (Figure 1D). To our surprise, we found the cardiac tumor mimicking myxoma had a complete fibrous capsule without myocardial infiltration and futher histological examination revealed primary cardiac large B-cell lymphoma (Figure 1E). The immunohistochemical markers showed strong positive staining for CD20, CD79a, Ki-67 (Figure 1E), and Bcl-2 in the malignant cells, and weak positive staining for CD3, CD31, Bcl-6, MUM-1, and c-Myc. The patient was discharged a few days later without chemotherapy treatment and was well after 6 months’ postoperative follow-up.