CASE PRESENTATION: A 40-year-old female patient was referred to our hospital with complaints of chronic diarrhea and intermittent lower abdominal pain for more than 10 years, and acute exacerbation that had commenced two weeks ago. Transthoracic echocardiography demonstrated right ventricular dilation and severe tricuspid valve regurgitation with an estimated right ventricular systolic pressure of 103mmHg. Computed tomography pulmonary angiogram showed a large filling defect within the main pulmonary trunk and extending into the right and left pulmonary arteries. The patient was failure to respond to thrombolytic therapy and presented with progressive dyspnea and abdominal distension. An emergency pulmonary endarterectomy was performed and found a whitish-yellow mass obstructed the lumen of the pulmonary artery, which was pathologically proved to be PAIS. No other hypermetabolic lesions except surgery sites were noted under 18F-fluorodeoxyglucose uptake in positron emission computed tomography. After surgery, the patient’s clinical condition improved and the diarrhea disappeared. But the sarcoma relapsed as an obstructive mass in the right pulmonary artery, a right adrenal gland metastatic lesion and a mass in right hilum were detected during follow-up phrase. The patient suffered symptoms as chest pain, shortness of breath and fatigue, no obvious diarrhea. Her clinical condition continued to deteriorate and could not undergo palliative operation. The patient passed away 17 months after surgery.