Imaging Clues to Distinguish Primary Pulmonary Artery Sarcoma from Pulmonary Embolism

Abstract

Introduction

Primary pulmonary artery sarcoma (PPAS) is a rare, aggressive tumor arising from mesenchymal cells in the intimal layer of the pulmonary artery. It frequently mimics pulmonary thromboembolism (PTE), often leading to delayed diagnosis and inappropriate treatment. Early identification is crucial due to its rapid progression and high mortality.

Case Report

A 36-year-old male presented with progressive dyspnea, lower limb edema, and jugular distension, following recent hospitalization for presumed acute PTE. Despite anticoagulation with rivaroxaban, symptoms worsened. Work-up revealed elevated N-terminal prohormone of brain natriuretic peptide (NT-proBNP), severe pulmonary hypertension on echocardiography, and no evidence of thrombophilia or infection. Chest computed tomography angiography (CTA) showed irregular, partially occlusive filling defects in the pulmonary arteries with perfusion defects. Positron emission tomography-computed tomography (PET-CT) revealed high fluorodeoxyglucose (FDG) uptake without metastases. Computed tomography-guided biopsy of a mediastinal lesion confirmed spindle-cell sarcoma (actin-positive, cytokeratin-focal positive, MDM2/ALK/CD34-negative), establishing the diagnosis of PPAS. The patient deteriorated due to right ventricular dysfunction from tumor obstruction. Despite stabilization with dobutamine and urgent chemotherapy (docetaxel/gemcitabine), surgical exploration revealed unresectable tumor infiltration. He succumbed to refractory hemodynamic collapse.

Discussion

Primary pulmonary artery sarcoma is often misdiagnosed as PTE, delaying appropriate care. Imaging—especially PET-CT and magnetic resonance imaging (MRI)—plays a pivotal role in distinguishing PPAS from thromboembolic disease. Findings such as heterogeneous soft-tissue filling defects, extravascular extension, and FDG avidity suggest malignancy. Histopathological confirmation remains essential. Unlike most cases diagnosed postmortem, our patient received an antemortem diagnosis, highlighting the importance of early oncologic suspicion in similar scenarios. Timely diagnosis may allow earlier interventions and improve outcomes. The present study was approved by the Research Ethics Committee of Hospital Beneficência Portuguesa de São Paulo (Approval No. 7.585.388 / CAAE 88073625.7.0000.5483), with waiver of informed consent due to its retrospective nature.

Keywords

pulmonary artery - sarcoma - pulmonary embolism - vascular - neoplasia

Introduction

Primary pulmonary artery sarcoma (PPAS) is a rare and aggressive malignant neoplasm originating from mesenchymal cells in the intimal layer of the pulmonary artery. We present a case initially diagnosed as pulmonary thromboembolism (PTE), in which clinical deterioration despite anticoagulation and imaging findings suggested malignancy, leading to a histological diagnosis of PPAS during life, contrasting with the majority of cases diagnosed postmortem.

Case Report

A 36-year-old man presented to the emergency department with worsening dyspnea at rest, tachycardia, jugular venous distension, and lower limb edema for 20 days. He reported a recent hospitalization for acute PTE four weeks earlier and was undergoing anticoagulation with rivaroxaban without clinical improvement. Upon admission, he was hemodynamically stable and denied comorbidities, smoking history, or other medications. Laboratory findings revealed elevated N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels (4,691 pg/mL), with no other significant abnormalities, including negative investigations for thrombophilia, rheumatologic, and infectious diseases. Transthoracic echocardiogram showed significant right ventricular (RV) enlargement, reduced tricuspid annular plane systolic excursion of 11 mm, pulmonary artery systolic pressure of 92 mmHg, and a thickened pericardium with moderate effusion, indicating severe pulmonary hypertension (PH). Lower extremity venous ultrasound was negative for deep vein thrombosis. Chest computed tomography angiography (CTA) revealed irregular, partially occlusive filling defects in the main pulmonary arteries, extending bilaterally to segmental and subsegmental arterial branches, with consequent perfusion defects in the lung parenchyma ([Fig. 1]). Chronic PTE, pulmonary artery neoplasm and fibrosing mediastinitis were considered the main differential diagnoses. Further evaluation with positron emission tomography-computed tomography (PET-CT) confirmed a neoplastic process, revealing very high radiotracer uptake in the filling defects, without distant lesions ([Fig. 1]). A biopsy of the mediastinal lesion was performed under CT guidance, but the patient developed a small pneumothorax and alveolar hemorrhage, which were hemodynamically managed in intensive care. Histopathology confirmed a spindle-cell sarcoma, actin-positive, focal cytokeratin-positive, MDM2-negative, Alk-negative, CD34-negative, leading to a final diagnosis of locally advanced PPAS.

Fig. 1 Admission arterial computed tomography angiography (A–C: axial plane in mediastinal window; (D) axial plane in lung window with minimal intensity projection reconstruction) show soft-tissue-like filling defects leading to a beaded appearance of the main pulmonary arteries (arrows in A and B), extending to subsegmental arteries in both lungs, with vascular distension by occlusive and non-occlusive defects and extravascular spread (arrows in C). Mosaic attenuation of the lungs is also seen (stars in D), owing to perfusion defects/oligemia. Positron emission tomography-computed tomography (E: axial fusion images) show intense fluorodeoxyglucose uptake in the filling defects (arrows in E), with a standard uptake value of up to 15.5.

During hospitalization, the patient experienced hemodynamic instability, hyperlactatemia, desaturation, and somnolence, interpreted as right ventricular dysfunction secondary to mechanical obstruction by the tumor. Dobutamine infusion stabilized his condition. Due to the severity and worsening perfusion, urgent chemotherapy with docetaxel and gemcitabine was initiated. However, with continued clinical deterioration, cardiovascular surgery was considered, and tumor resection was attempted. Intraoperatively, the tumor was found to be unresectable due to diffuse infiltration into the right pulmonary artery, and the patient succumbed to refractory hemodynamic complications.

Discussion

Primary pulmonary artery sarcoma is an exceedingly rare and aggressive malignancy, with an estimated global incidence of 0.001 to 0.03%.[1] It exhibits a female predominance (2:1), with most cases diagnosed in the 5^th to 6^th decades of life.[2] The clinical presentation is variable, depending on tumor size and location, including constitutional symptoms, dyspnea, chest pain, cough, hemoptysis, and complications such as atrial or ventricular tachyarrhythmias, conduction abnormalities, pericardial effusion, and cardiac tamponade.[3]

Primary pulmonary artery sarcoma often mimics PTE, leading to a delayed diagnosis and inappropriate anticoagulation management in approximately 47% of cases,[1] contributing to a high mortality rate.[2] [4] Accurate differential diagnosis is critical due to the tumor's aggressiveness and rapid progression to pulmonary hypertension, right heart failure and death, if untreated.[5] The prognosis of PPAS is poor, with survival ranging from 12 to 18 months from symptom onset and a mean survival of fewer than 2 months without surgical intervention.[1]

The initial diagnosis and precise tumor burden definition rely primarily on imaging.[3] CTA, magnetic resonance angiography, and PET-CT are essential for differentiating PPAS from PTE.[1] Imaging features suggestive of PPAS include hyperdense lesions with non-homogeneous attenuation due to hemorrhage, a “beaded” appearance of the pulmonary arteries, filling defects with soft-tissue characteristics, distal oligemia, vascular distension, and extravascular spread.[3] Primary pulmonary artery sarcoma can extend into the main pulmonary trunk and right ventricular outflow tract, occupying the entire lumen with local aneurysmal dilation and forming acute angles with the vessel wall.[1] Unlike PTE, PPAS tumors typically have lobulated, bulging margins, whereas thromboemboli exhibit straight, cup-shaped margins. Additionally, distal invasion of the lung parenchyma suggests malignancy.[6] The “wall eclipsing sign” on CTA, characterized by near-complete occlusion of the pulmonary artery and lesion extension beyond the vessel wall, is highly indicative of PPAS.[1] The majority of these findings were observed in our case, as identified in the figure.

Cardiac MRI has become the preferred imaging modality for PPAS due to its superior anatomical resolution and tissue characterization capabilities, distinguishing PPAS from PTE. Gadolinium-enhanced MRI helps differentiate tumors from thrombi, with the degree of enhancement correlating with tumor differentiation. This feature is also valuable for follow-up and evaluating locoregional recurrence. Functional assessment, including flow and pressure gradients across the pulmonary vasculature, also aids in diagnosing PPAS.[3]

Similar to gadolinium-enhanced MRI, FDG uptake on PET-CT can differentiate PPAS from PTE, as FDG activity is more intense in malignancies.[1] Positron emission tomography-computed tomography is also useful for staging purposes, although FDG uptake near the RV may be confounded by myocardial activity.[3] In our case, PET was essential in corroborating the diagnosis and guiding the biopsy site.

Despite the use of various imaging modalities suggesting a diagnosis of PPAS, histopathological confirmation remains essential for a definitive diagnosis. Given the severity of the condition, many cases only receive an etiological diagnosis during post-mortem evaluation.[2] [7] In our reported case, the prompt suspicion of an oncological diagnosis at admission, followed by subsequent imaging studies, allowed for a CT-guided biopsy and the diagnosis of sarcoma while the patient was still alive, enabling treatment proposals. This underscores the importance of early identification in similar clinical and imaging settings, in which a swift diagnosis can facilitate earlier interventions, ultimately improving patient outcomes.[3] [8]

Conflict of Interests

The authors have no conflict of interests to declare.

Authors' Contributions

FMC and MTC: conceptualization, project administration, methodology, data curation, and writing – review & editing; MCP, CRS, and VFC: conceptualization, project administration, methodology, data curation, and writing – original draft.

• References

• 1 Kronzer E, Robinson SI, Collins DA, McBane II RD. Primary pulmonary artery sarcoma versus pulmonary thromboembolism: a multimodal imaging comparison. J Thromb Thrombolysis 2021; 52 (04) 1129-1132 PubMed
• 2 Wong HH, Gounaris I, McCormack A. et al. Presentation and management of pulmonary artery sarcoma. Clin Sarcoma Res 2015; 5 (01) 3
• 3 Wyler von Ballmoos MC, Chan EY, Reardon MJ. Imaging and surgical treatment of primary pulmonary artery sarcoma. Int J Cardiovasc Imaging 2019; 35 (08) 1429-1433
• 4 Dornas APAV, Campos FTAF, Rezende CJ, Ribeiro CA, Amaral NF, Corrêa RdeA. Intimal sarcoma of the pulmonary artery: a differential diagnosis of chronic pulmonary thromboembolism. J Bras Pneumol 2009; 35 (08) 814-818
• 5 Bandyopadhyay D, Panchabhai TS, Bajaj NS, Patil PD, Bunte MC. Primary pulmonary artery sarcoma: a close associate of pulmonary embolism-20-year observational analysis. J Thorac Dis 2016; 8 (09) 2592-2601
• 6 Fernandez R, Edgren D, Bharat A. Pulmonary artery sarcoma. Am J Respir Crit Care Med 2017; 195 (03) e23-e24
• 7 Yi CA, Lee KS, Choe YH, Han D, Kwon OJ, Kim S. Computed tomography in pulmonary artery sarcoma: distinguishing features from pulmonary embolic disease. J Comput Assist Tomogr 2004; 28 (01) 34-39
• 8 Ito S, Tahara N, Fukumoto Y. Refractory pulmonary artery intimal sarcoma. Eur Heart J 2023; 44 (36) 3484

Publication History

Received: 01 June 2025

Accepted: 10 October 2025

Article published online:
22 December 2025