[A Case of De Novo Stage Ⅳ Her2-Positive Breast Cancer with Cardiac Tamponade Caused by Cancerous Pericarditis].

The patient was a 58-year-old woman. She was diagnosed with cT4b, cN3c, cM1, cStage Ⅳ, Her2 positive breast cancer with liver, lung and bone metastases. Seven days after the first visit, she came to our hospital for dyspnea. Chest X-ray, chest CT, and echocardiography showed a decrease in EF to 50.6% due to a large amount of pericardial effusion, and she was diagnosed with cardiac tamponade. On the same day, pericardial drainage was performed urgently. The cytopathology of pericardial fluid was malignant, that is to say, she was diagnosed with cancerous pericarditis. Pericardial drainage relieved respiratory distress, and echocardiography showed disappearance of pericardial fluid and improvement of EF up to 80.4%. Docetaxel plus trastuzumab plus pertuzumab therapy was started 10 days after pericardial drainage as first-line treatment. After starting chemotherapy, the response has continued for 6 months without re-accumulation of pericardial fluid.