ABSTRACT
Introduction: Cardiac lymphoma is a rare but serious disease that is usually located in the right heart. The symptoms (dyspnea, respiratory distress, fatigue, syncope ) are not specific and depend on the mass location. Cardiac magnetic resonance has a crucial role in the diagnostic strategy but biopsy is mandatory to confirm the diagnosis. Case presentation: We report the case of a 63-yeart old man who presented with severe dyspnea and complete atrioventricular block (AVB). A bulky and invasive mass was found in the left atrium extending to the right atrium through the interatrial septum. A cardiac lymphoma was suspected by cardiac magnetic resonance (CMR) imaging and confirmed by transvenous biopsy. The patient was treated with urgent chemotherapy (R-CHOP) and pacemaker implantation. After 4 cycles of R-CHOP the patient was in complete remission with total disappearance of the mass and return of a spontaneous sinus rhythm. Conclusion: lymphoma is a therapeutic emergency as appropriate treatment can lead to complete remission even when the mass is extensive and invasive. Complete AVB is a potentially reversible complication of cardiac lymphoma, and the decision to implant a pacemaker must be carefully weighed.