Metastatic cardiac tumor presenting as atrial fibrillation in a previously healthy woman

Rationale: Metastatic cardiac tumor (MCT) is rare in clinical practice. MCT presenting initially as atrial fibrillation (AF) is even rarer. Patient concerns: We report a 47-year-old woman with no previous medical history presented with intermittent palpitation for 3 days. Diagnoses: The electrocardiography showed AF with rapid ventricular rate. The transthoracic echocardiography showed a 4 × 4 cm mass occupying the left atrium (LA). The contrast enhanced computed tomography (CT) showed a left lower lung mass with invasion to the LA and left upper pulmonary vein (PV). The chest CT guided biopsy revealed poorly differentiated squamous cell carcinoma. Further workup including bone scan showed no significant findings. The diagnosis of lung squamous cell carcinoma with cardiac invasion was made. Interventions: She went on to received palliative chemotherapy. Outcomes: She is being followed up regularly at the outpatient department. Lessons: Tumor invasion of the LA and PV was thought to be the cause of the AF. This condition is rare, but clinically important. Physicians should be alert that MCT could be an important differential diagnosis in patients presenting with unexplained AF.