A rare case report of pulmonary artery sarcoma diagnosed and managed based on multimodal imaging

Abstract

Background

Pulmonary artery sarcoma (PAS) is a rare malignant tumour of pulmonary vessels. Due to the lack of specific clinical symptoms, PAS is easily misdiagnosed as pulmonary thromboembolism, so that many patients miss the opportunity of early diagnosis and treatment.

Case summary

A 42-year-old man presented to the hospital with a heart murmur on physical examination. After admission, he underwent serial imaging studies and was diagnosed with a pulmonary artery mass. Guided by multimodal imaging, the patient underwent surgical treatment, and post-operative pathology confirmed the diagnosis of PAS. Eighteen months after the operation, the patient’s follow-up examination results indicated tumour recurrence.

Discussion

This case emphasizes the advantages of combining multiple imaging modalities in the early identification of PAS and in guiding surgical management.

Learning points.

• Multimodal imaging (echocardiography, CTPA, CMR, and FDG-PET/CT) is essential to differentiate pulmonary artery sarcoma (PAS) from acute pulmonary thromboembolism.

• The presence of heterogeneous late gadolinium enhancement on CMR and high FDG uptake on PET/CT are key features favouring malignancy over thrombus.

• Complete surgical resection remains the cornerstone of treatment for PAS, and close long-term follow-up for distant metastasis is absolutely necessary.

Introduction

Pulmonary artery sarcoma (PAS) is a rare malignant tumour of pulmonary vessels. Due to the lack of specific clinical symptoms, PAS is easily misdiagnosed as pulmonary thromboembolism (PTE); thus, many patients miss the opportunity for early diagnosis and treatment.¹ This article reports a rare case of PAS diagnosed and managed based on multimodal imaging [echocardiography, computed tomographic pulmonary angiogram (CTPA), cardiac magnetic resonance imaging (CMR), and fluorine-18 fludeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT)], in order to highlight the advantages of combining multiple imaging modalities in the early identification of PAS and in guiding surgical management.

Summary figure

Case report

A 42-year-old man with no history of smoking or alcohol use, but with a medical history of hyperlipidaemia for 8–10 years, presented with intermittent palpitations on exertion for 1 year. He sought consultation after a heart murmur was detected during a physical examination 2 months earlier. On admission, physical examination revealed a grade 4/6 systolic murmur in the pulmonary valve auscultation area. Bilateral lung auscultation revealed clear breath sounds without audible dry or wet rales. To investigate the cause, transthoracic echocardiography was performed, revealing severe tricuspid regurgitation, mild pulmonary hypertension, and irregular masses within the right ventricular outflow tract (RVOT) and pulmonary artery (PA) (Figure 1A). The largest mass, located within the main PA, measured ∼22 × 38 mm. The pulmonary valve was not clearly visualized, suggesting possible involvement. Tumour markers were within normal limits, and other routine laboratory tests showed no significant abnormalities. The electrocardiogram demonstrated sinus rhythm with right axis deviation.

Figure 1.

Transthoracic echocardiography shows a mass (arrow) within the pulmonary artery (A). Computed tomographic pulmonary angiogram showing multifocal masses (arrows) in the right ventricular outflow tract, main pulmonary artery, and right pulmonary artery (B). Cardiac computed tomography revealing multiple masses (arrows) in the right ventricle, main pulmonary artery–left pulmonary artery, and right pulmonary artery (C). Cardiac cine imaging shows masses (arrow) in the right ventricular outflow tract and pulmonary artery (D). Cardiac T2-weighted double inversion-recovery sequence shows a T2-hyperintense mass (arrow) in the right ventricular outflow tract (E). Cardiac magnetic resonance imaging with late gadolinium enhancement shows intense heterogeneous late gadolinium enhancement (F).

Given the patient’s age and the imaging manifestations of transthoracic echocardiography, the differential diagnosis included acute pulmonary embolism (PE) and primary PA malignancy. However, the absence of risk factors for venous thromboembolism, the lack of response to empirical anticoagulation, and the broad-based attachment of the mass to the vessel wall on echocardiography raised suspicion for PAS.

To further confirm the diagnosis and guide clinical treatment, the patient underwent serial imaging studies. To rule out PE, the patient underwent laboratory tests that revealed D-dimer 132 ng/mL (<243 ng/mL). The laboratory test results were not consistent with PE. Moreover, a CTPA was performed, which revealed multifocal irregular soft-tissue masses in the RVOT, main PA, and right PA, extending to the left upper PA, with adjacent left lung consolidation (Figure 1B). The largest mass, located in the main PA and involving the pulmonary valve, measured ∼40 × 28 × 22 mm. The CTPA report suggested the high probability of malignancy, with no evidence of mediastinal invasion. Cardiac CT was subsequently performed to better assess the extent of the mass and guide surgical planning. Cardiac CT revealed multiple masses in the right ventricle, main PA–left PA junction, and right PA, involving the left superior PA (Figure 1C). There was no involvement of other cardiac structures except the right ventricle. No feeding vessels supplying the masses were visualized. To further characterize the lesions and assess their impact on cardiac structure and function, CMR was performed. Cardiac magnetic resonance imaging revealed masses in the RVOT and PA (Figure 1D and E), with dilation of the right atrium and right ventricle, myocardial injury at the left ventricular insertion points, and tricuspid insufficiency. The masses were isointense on T1WI, slightly hyperintense on T2WI, and hyperintense on fat-suppression T2WI. Late gadolinium enhancement (LGE) showed intense heterogeneous LGE consistent with viable tumour tissue (Figure 1F). The left ventricular ejection fraction was 65.9%, with preserved systolic and diastolic function. To evaluate for distant metastasis and determine the clinical stage, an integrated FDG-PET/CT scan was performed. It demonstrated hypermetabolic lesions (maximum standardized uptake value of 7.6) in the RVOT and main PA, without evidence of distant metastases (Figure 2A and B).

Figure 2.

Fluorine-18 fludeoxyglucose positron emission tomography/computed tomography revealing hypermetabolic lesions (intersection of two lines and black arrow) in the right ventricular outflow tract and main pulmonary artery, without distant metastases (A, B). Histopathology indicated that the tumours in the pulmonary artery and right ventricle were consistent with pulmonary artery sarcoma. Microscopically, tumour cells were spindle-shaped and arranged in a crisscross pattern. There was marked atypia, mitoses, multifocal calcification, and arterial intimal involvement. Eosin staining microscopy, magnification 10 × 20 (C). Repeat computed tomographic pulmonary angiogram identifies a recurrent right ventricular outflow tract mass (solid arrows) and multiple parenchymal nodular opacities (dashed arrow) in the upper lobe of the left lung (D).

Following pre-operative evaluation, the patient underwent complete resection of the PA and RVOT masses with pulmonary valve reconstruction using autologous pericardium. Post-operative vital signs were stable, and the patient was transferred to the intensive care unit. Histopathological examination (Figure 2C) confirmed PAS, with immunohistochemistry positive for MDM2/CDK4. The pathological diagnosis was consistent with the multimodal imaging findings, highlighting the diagnostic value of multimodal imaging in PAS. The patient received anticoagulation therapy with rivaroxaban after surgery. Subsequently, the patient received five cycles of ifosfamide and epirubicin chemotherapy within 6 months after surgery.

Six months after surgery, the patient returned for follow-up without chest pain, dyspnoea, haemoptysis, or other symptoms. Repeat CTPA demonstrated pulmonary emboli within branches of the left superior PA. Ventilation-perfusion scanning revealed perfusion defects in 24% of lung volume. Right heart catheterization confirmed precapillary pulmonary hypertension, leading to a diagnosis of chronic thromboembolic pulmonary hypertension. The patient improved following anticoagulant therapy with rivaroxaban.

Eighteen months post-operatively, repeat echocardiography showed recurrent RVOT masses, severe tricuspid regurgitation, and mild pulmonary hypertension. Repeat CTPA revealed recurrent RVOT masses, multiple parenchymal nodular opacities in the left lung, suggestive of metastatic recurrence (Figure 2D).

Discussion

Pulmonary artery sarcoma is a rare malignancy arising from mesenchymal cells between the RVOT and PA.² Pulmonary artery sarcoma is highly aggressive and carries a poor prognosis. Its global incidence is between 0.001% and 0.03%.³ Because symptoms such as cough, dyspnoea, and chest pain, as well as imaging features, often resemble those of PE, PAS is frequently misdiagnosed.³ Echocardiography can assess RVOT masses, pulmonary valve involvement (seen in ∼30% of cases), and pulmonary hypertension.⁴ On CTPA, PAS often appears as a vascular filling defect mimicking PE. In this case, however, CTPA accurately identified a PA mass, underscoring its diagnostic value. Cardiac magnetic resonance imaging can determine the extent of PAS and assess pulmonary valve involvement and has become the preferred modality for differentiating PAS from PE, as sarcomas typically show gadolinium enhancement whereas thrombi do not.⁵ This pattern of intense, heterogeneous LGE is a key discriminator from PTE, which typically shows no enhancement or only peripheral enhancement due to organized thrombus. Moreover, 18F-FDG PET/CT can distinguish PAS from PTE based on SUVmax values,⁶ with SUVmax > 2.9 being a reliable marker of malignancy.⁶ This case demonstrates that combining echocardiography, CT pulmonary angiography, cardiac CT, CMR, and PET/CT improves diagnostic accuracy, delineates lesion extent, and guides surgical planning.

Complete surgical resection combined with adjuvant or neoadjuvant chemotherapy is considered the standard treatment for PAS.⁵ However, despite comprehensive therapy, the overall prognosis remains poor (1.5 months without treatment vs. 8–36 months with treatment).⁵ This case highlights the aggressive nature of PAS, with recurrence and metastasis occurring despite multimodal therapy.

Conclusion

Pulmonary artery sarcoma is a rare malignancy with poor prognosis. In this case, PAS was suspected on the basis of multimodal imaging and confirmed by post-operative pathology. The findings emphasize the advantages of combining multiple imaging modalities in the early identification of PAS and in guiding surgical management. Early diagnosis and timely surgical treatment may improve patient outcomes.

Lead author biography

Kun Jiang is a graduate student at the Capital Medical University in Beijing, China. His research interest is in cardiovascular radiology.

Author contributions

Kun Jiang (Investigation, Writing—original draft [lead]), Hongkai Zhang (Resources [supporting], Writing—review & editing [lead]), Yao Lu (Resources [supporting]), Rui Liu (Resources [supporting]), and Lei Xu (Funding acquisition, Project administration [lead])

Consent: The authors confirm that the written consent for submission and publication of this case report, including images and associated text, has been obtained from the patient in line with COPE guidance.

Ethics statement: The authors confirm that the research reported has adhered to the relevant ethical guidelines.

Funding

This work was supported by Beijing Natural Science Foundation (7244326) and National Key Research and Development Program of China (2022YFE0209800).

Data availability

The data underlying this article will be shared on reasonable request to the corresponding author.