Primary cardiac lymphoma is rare. It can present with a wide variability of clinical symptoms frequently leading to a delay in diagnosis. We report a case of a primary cardiac lymphoma in a 85 year old woman. The MRI showed a large mass in the right atrio-ventricular groove and infiltration of the interventricular septum and left ventricular wall with subtle contrast enhancement, isointense aspect on T1 weighted and hyperintense aspect on T2 weighted sequences. Mostly the radiological signs are non specific. Calcification, hemorrhage, a diffuse infiltrative pattern with infiltration of the valves and coronary arteries and a left atrial localization can suggest the diagnosis.