Intracardiac recurrent thymoma arising from the coronary sinus

A 57-year-old woman was admitted with a short history of exertional breathlessness. Six years previously, she had a stage III malignant thymoma debulked, with adjuvant chemotherapy and radiotherapy for metastatic pleural disease, and had remained well following the procedure. A computed tomography scan of the chest (Figure 1A) documented recurrent pleural metastases, as well as a large mass in her right atrium (white arrow) with a dilated coronary sinus (black arrows). Transthoracic echocardiography demonstrated a restrictive cardiomyopathy on mitral inflow pulsed-wave Doppler (Figure 1B). It also showed a highly mobile mass prolapsing through her tricuspid valve. A magnetic resonance image of the heart (Figure 1C) confirmed a 70 mm × 40 mm right atrial mass with significant thickening of the lateral left ventricular (LV) wall (green arrow), believed to represent metastatic infiltration. The mass was surgically removed (Figure 1D) and found to be originating from the coronary sinus. The lateral LV wall was infiltrated by a tumour, and histology of the mass confirmed it to be a metastatic thymoma.

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Figure 1)

LA Left atrium; LV Left ventricle; PM Pleural metastasis; RA Right atrium; RV Right ventricle

Intracardiac masses are mainly due to tumours, thrombi or vegetation. Intracardiac thymoma is a rare feature (1), with previous cases reported of metastatic spread to the right atrium, typically originating from the vena cava (2). To our knowledge, the present report is the first to describe an intracardiac recurrent thymoma arising from the coronary sinus, via infiltration from the lateral LV wall by pleural metastases. The present case also highlights how the use of several different noninvasive imaging modalities can be helpful in clarifying a rare diagnosis.

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