Dear Editor, Primary cardiac lymphoma is a rare malignant lymphoma of the heart and pericardium [1, 2]. Delayed diagnosis is an ominous prognostic factor because of the non-specific initial presentation and rapid progression of this disease [3–7]. An 82-year-old woman with atrial fibrillation was prescribed amiodarone since early June 2009. In July 2009, she experienced dizziness, palpitation, and exertional dyspnea. Electrocardiography (ECG) revealed atrial fibrillation with slow ventricular rate (30–40/min). Amiodarone-induced arrhythmia was suspected initially, and then amiodarone was discontinued for more than 3 weeks. However, she continued experiencing dizziness occasionally and electrocardiography revealed junctional bradycardia. The patient was admitted to our cardiovascular ward. Holter ECG revealed a prolonged sinus pause (>3 s). Echocardiography showed left atrial dilatation (Fig. 1a). A permanent pacemaker was implanted via the left subclavian vein. Five days later, echocardiography (transthoracic and transesophageal) revealed a mass-like lesion, which was not observed 2 months earlier, in the right atrial appendage (Fig. 1b). The lesion was suggestive of a thrombus that was associated with pacemaker implantation. The patient was prescribed anticoagulants and thrombolytic agents. However, a series of echocardiographies performed during the treatment period revealed poor response. After 4 weeks, computed tomography (Fig. 1c) revealed a filling defect in the heart and bilateral pleural effusion. To investigate the cause of the intracardiac mass, we performed an operation in September 2009. Subtotal removal of the masses was performed because total resection was impossible. Pathologic examination revealed (Fig. 1d) large B cell lymphoma. Bone marrow examination showed no invasion of the lymphoma cells. Positron emission tomography revealed a diffuse linear pattern of fluorodeoxyglucose (F-FDG) uptake in the cardiac recess; FDG uptake was not observed in any other region. Physical examination did not reveal palpable lymphadenopathy or other mass lesions. The patient refused further treatment after the operation. However, she developed progressive orthopnea and exertional dyspnea in early October 2009. Follow-up echocardiography revealed enlargement of the heart mass. The patient received a series of systemic chemotherapy, including one cycle of COP (cyclophosphamide, vincristine, and prednisolone) followed by seven cycles of R-CHOP (rituximab, cyclophosphamide, anthracycline, vincristine, and prednisolone) until April 2010. The latest echocardiS.-F. Cho : S.-F. Lin Division of Hematology & Oncology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan