A 61-year-old man was referred to us for palpitations and ventricular tachycardia. After being treated by chemotherapy for a mediastinum lymphoplasmocytic lymphoma, a ventricular tachycardia (VT) occurred. It was well tolerated. Several imaging techniques showed that this VT was related to a tumoural infiltration of the anterior part of the right ventricle by the lymphoma. Ventricular arrhythmias were controlled under antiarrhythmic drugs and chemotherapy was continued, with close cardiac follow-up. Complete remission was reached with restoration of a normal right ventricular function and resolution of the ventricular arrhythmias.