An 82-year-old woman with a cardiac mass.

CLINICAL INTRODUCTION: An 82-year-old woman suspected of a cardiac tumour was referred for evaluation. Patient's medical history included atrial fibrillation, implantation of a VVI (ventricular stimulation) pacemaker 3 years earlier due to advanced atrioventicular (AV) block, arterial hypertension and hypothyroidism. Patient was adequately anticoagulated with warfarin (international normalized ratio (INR) 3.0 at admission). She reported occasional palpitations and a 2 kg weight loss in the last 2 years, but denied shortness of breath, chest pain, malaise, fever, chills or cough. Blood samples were taken for tests and cultures. Red blood cells, haemoglobin, white blood cells, platelets, C- reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were within normal ranges. Blood cultures were negative. Echocardiogram (figure 1A) (see online supplementary videos 1 and 2) and cardiac CT were performed (figure 1B).

QUESTION: Which of the following is the most likely diagnosis?Caseous calcification of the mitral annulusCoconut left atriumMitral valve myxomaPeriannular abscess.