Primary cardiac tumours are very rare. We describe the case of a 69-year-old female suffered from metastatic breast cancer and intestinal polyposis. During periodical follow-up examinations, total body Computed Tomography showed a right atrial mass with heterogeneous contrast enhancement, located near the orifice of inferior vena cava. The trans-thoracic and trans-esophageal echocardiogram confirmed the diagnosis. Thrombus or cardiac metastatic localization was the two principal hypotheses even if the CT scan suggested that was a myxoma. Surgical resection was performed expecially for the high risk of the mass' embolization. The hystological examination confirmed the CT scans suspiction of cardiac myxoma. The patient was discharged from hospital without any complications. After 6 months, she was fine.