The heart is the rarest site for neoplasms to be localized. Despite modern diagnostic techniques, cardiac tumours continue to among those discovered latest and with the worst prognoses. We present the case of a 62-year-old woman with a heart tumour and mediastinal lymphadenopathy, who was admitted to the Department of Cardiac Surgery. The patient underwent surgical removal of the tumour with extracorporeal circulation. The left atrium, mitral valve and the left ventricle were occupied by the infiltration. A radical resection appeared to be impossible. A valvular prosthesis was not implanted. The perioperative period was uncomplicated. On the 9th day a local recurrence was confirmed in the transthoracic echocardiography. Further oncological diagnostics revealed the spread of the malignant neoplasm to bones of the pelvis and spine. Chemotherapy was initiated. The authors discuss the most appropriate diagnostic and treatment procedures employed in the above case.