Pulmonary tumor thrombotic microangiopathy (PTTM) is a high-mortality disease that is difficult to diagnose clinically. Our patient was an 80-year-old woman who came to us due to symptoms of increasing dyspnea. A clinical evaluation showed that she had hypoxemia and pulmonary arterial hypertension without any abnormalities in the major pulmonary arteries, bronchi, or alveoli. A lung perfusion scan showed multiple wedge-shaped perfusion defects. Further examination revealed adenocarcinoma in her right parotid gland with metastasis to the submandibular lymph nodes. We diagnosed her to have PTTM caused by a parotid tumor. The patient survived for 11 months with chemotherapy. An early antemortem diagnosis by minimally invasive examinations will help PTTM patients to survive longer.