Pulmonary tumor thrombotic microangiopathy(PTTM)caused by pulmonary artery microscopic tumor emboli and fibrocellular and/or fibromuscular proliferation leads to progressive pulmonary hypertension and respiratory failure.The prognosis is extremely poor and most patients die shortly after onset.We report a patient with Stage IV breast cancer and long-term survival who developed PTTM during chemotherapy treatment.A 63-year-old woman with multiple metastases in her cerebellum, bone, lung, and lymph node after left breast conserving surgery started to experience dyspnea and malaise 7 years after the surgery.Two months later, she was urgently admitted to hospital because of respiratory failure and was diagnosed with pulmonary hypertension.However, pulmonary thrombosis and tumor thrombus were not observed.We clinically diagnosed her with PTTM and administered chemotherapy in addition to treatment for pulmonary hypertension.Her medical condition improved gradually and she survived for the subsequent 2 years.When observing progressive hypoxia and pulmonary hypertension without obvious pulmonary embolism findings on imaging, PTTM should be considered.Early diagnosis and immediate induction of chemotherapy for primary disease can improve the survival of patients with PTTM.