Two of the patients with PAS had lower extremity DVT, indicating that the presence of DVT does not rule out PAS. The mean Wells score was 4.5961.90 and the mean revised Geneva score was 1.3961.21 in patients with PAS, indicating a low probability of acute pulmonary thromboembolism. These scores may help to differentiate between PAS and thromboembolic lesions. As it is usually not possible to differentiate between PAS and acute or chronic thromboembolic disease based on clinical findings, patients are initially treated with anticoagulant therapy or even thrombolysis. No studies evaluating outcomes after longterm anticoagulant therapy in patients with PAS have been reported. However, many case reports suggest that failure of anticoagulant therapy to improve the patient’s condition should raise the suspicion of PAS, and should lead to early consideration of biopsy or surgery to confirm the diagnosis, and early treatment to prolong survival. Imaging Saikosaponin-C examination findings are very Atractylenolide-III useful for diagnosing PAS. Chest radiography findings are always nonspecific in 
PAS patients. Ventilation-perfusion scintigraphy is of limited value in differentiating PAS from thromboembolic disease. Several reports suggest that PACTA and MRI may be the most useful investigations for differentiating between tumor and thrombosis. PACTA findings are similar in PAS and thromboembolic disease, and are characterized by filling defects in the pulmonary vessels. Enhancement of the lesion on gadolinium-MRI indicates a tumor, as a non-vascularized intraluminal thrombus does not enhance after injection of gadolinium. No information regarding enhancement in patients with sarcoid infiltration of the pulmonary artery was found in the literature; however, 80% of patients with active infiltrative lung disease have positive MRI findings. The radiologist is usually the first to raise the suspicion of PAS in patients with severe dyspnea and pulmonary artery filling defects who are unresponsive to anticoagulant therapy. Combined CT and PET-CT findings are very useful for assessing patients with suspected PAS. Early diagnosis with the help of integrated imaging examination findings is the main factor required to obtain improvements in prognosis. In this study, PACTA findings were useful for differentiating between PAS and pulmonary embolism. The characteristics suggestive of PAS include a filling defect occupying the entire lumen of the pulmonary trunk with an increase in diameter of the involved vessel and delayed patchy contrast enhancement, which is more evident in the venous phase. PET-CT was performed to differentiate between PAS and APE based on the intensity of contrast enhancement. MRI was also sometimes performed in patients with equivocal results on PET-CT, to improve tissue characterization of the lesions and differentiate between thromboembolism and neoplasm. Based on preoperative imaging examination findings, nine patients were thought to have CTEPH, and only three were correctly diagnosed with PAS based on PET-CT findings. However, this retrospective study found that all 12 patients with PAS had the wall eclipsing sign, and that all patients with APE and CTEPH did not have this sign. We therefore consider the wall eclipsing sign on PACTA to be pathognomonic for PAS. When the wall eclipsing sign is observed, further investigations should be performed to confirm PAS, or the lesion should be resected. All the patients in our series were inappropriately treated with thrombolytic/anticoagulant therapy for a mean period of 5.563.7 months, and some of them suffered severe complications due to long-term anticoagulant therapy or thrombolysis such as gastric bleeding, heparin-induced thrombocytopenia, and liver injury.