A 74-year-old man was referred to the outpatient clinic of the cardiology department with progressive dyspnoea and a new heart murmur. Physical examination of the chest wall showed a hard immobile and painless sternal swelling at the level of the angulus of Ludovici. There was an increase of the velocities across the pulmonary valve (continuous Doppler) on echocardiography as a result of the RVOT and pulmonary trunk stenosis. Computed tomography (CT) of the chest revealed a mass in the anterior mediastinum which had grown through the sternum into the skin, as well as an external compression of the ascending aorta, the truncus pulmonalis and the pericardium. Anatomo-pathological examination revealed a non-small-cell lung carcinoma. PET CT showed another nodule with FDG uptake in the right kidney, suspected for metastasis, and an uptake in a right paratracheal lymph node. The tumour was staged as a cT4cN2M1b. Palliative radiochemotherapy was started. The patient had a good clinical and radiographic response, but relapsed a few months later.