Unresolved pulmonary embolism leading to a diagnosis of pulmonary artery sarcoma

Chronic inflammatory pulmonary artery lesion causing right pulmonary artery stenosis 15 years post Blalock-Taussig shunt ligation

Discrete central endovascular pulmonary arterial lesions raise clinical concern for malignancy such as primary pulmonary artery sarcoma. We present a case of a female in her late teens who had an obstructive mid right pulmonary artery lesion found on follow-up imaging 15 years after Tetralogy of Fallot repair. The lesion was in the vicinity of a previously ligated Blalock-Taussig shunt and causing right PA stenosis with delayed perfusion to the right lung, and a flow-related distal left PA aneurysm. The lesion was excised and confirmed histologically to be inflammatory in nature. Intraoperative microbiology demonstrated growth of the Kytococcus species, and she was managed with 6 weeks of intravenous antibiotics, with a full recovery.

Pulmonary artery sarcoma masquerading as pulmonary embolism: an under-recognised entity

Pulmonary artery sarcoma is a rare disease with only a handful of cases reported. It is histologically classified as leiomyosarcoma, spindle cell sarcoma, fibrous histiocytoma or undifferentiated sarcoma. The disease is mostly misdiagnosed as pulmonary thromboembolism and carries a grim prognosis with an average survival of only a few months. Misdiagnosis often results in patients being treated inappropriately and diagnosed in later stages of the disease. This delay in diagnosis can be associated with significant mortality in the setting of an already poor prognosis. Early aggressive surgery targeting complete surgical resection is the standard treatment. Chemotherapy and radiation therapy have been tried with variable outcomes. Given the aggressive nature of pulmonary artery sarcoma, regular post-surgery follow-up is indicated.

The filling defect of pulmonary artery, an imaging finding what we should know

The most common cause of pulmonary artery filling defects on computed tomography pulmonary angiography or magnetic resonance imaging is pulmonary thromboembolism, but not infrequently, the presentation of this finding lacks specificity. Given that the morbidity and mortality associated with pulmonary thromboembolism is high, proper diagnosis of the condition is essential. Unusual or more rarely encountered etiologies must be considered when clinical manifestations and imaging findings are inconsistent. With this review, our purpose is to describe possible causes of pulmonary arterial filling defects. We aim to provide clinicians with a comprehensive list of differential diagnoses to facilitate a measured approach to the assessment of pulmonary arterial filling defects on computed tomography pulmonary angiography or magnetic resonance imaging.

Intraluminal Arterial Filling Defects Misdiagnosed as Pulmonary Emboli: What Else Could They Be?

Pulmonary artery filling defects can be observed in various pathologic processes other than pulmonary embolism, for example, nonthrombotic pulmonary embolism with biological and nonbiological materials and intrinsic pulmonary artery lesions. They have also been described in rare conditions, such as fibrosing mediastinitis and congenital absence or stenosis of pulmonary artery, and some pulmonary parenchymal and airway malignancies. Misdiagnosis is common owing to the relative rarity of these conditions. Correct diagnosis is based on the appropriate clinical suspicion considering the unique clinical features, laboratory findings, and additional radiologic clues inferring a pathology other than pulmonary embolism.

Differential Diagnosis of Pulmonary Artery Sarcoma and Central Chronic Pulmonary Thromboembolism Using CT and MR Images

BACKGROUND

Clinical and imaging manifestations are similar in pulmonary artery sarcomas (PAS) and thromboembolic diseases, especially central chronic pulmonary thromboembolism (CPTE). The feasibility of utilising clinical imaging tools such as computed tomography (CT) and magnetic resonance imaging (MRI) for differential diagnosis of PAS and CPTE has not been fully explored, especially MRI.

METHODS

Patients with PAS (n=18) and central CPTE (n=20) treated at our hospital between January 2013 and September 2016 were identified retrospectively. Computed tomography and MRI findings of pulmonary artery (PA) filling defects including the location, the involvement of pulmonary artery, morphology, signal intensities and enhancement in MRI, calcification, sizes of right atrium and ventricle, inner diameters of the pulmonary artery trunk and branches, and mediastinal collateral circulation in both groups were examined, and differences were analysed by Fisher exact test and independent sample t-test.

RESULTS

Compared to those of central CPTE, PAS lesions were in full shape or expansive growth (p<0.001), and the proximal end of the tumours was often bulging or lobulated (p<0.001). These lesions were aneurysm- or grape-like distally (p<0.01) with inhomogeneous enhancement (p<0.001). The MRI contrast enhancement pattern of PAS lesions were cloudy with inhomogeneous delayed enhancement and the time-density curves for some of the lesions increased gradually.

CONCLUSION

Computed tomographic and MR imaging manifestations may resemble PAS and central CPTE; however, some manifestations still have great value for the differential diagnosis of these two conditions, specifically the morphology and MRI enhancement patterns.

When a pulmonary embolism is not a pulmonary embolism: a rare case of primary pulmonary leiomyosarcoma

Arterial leiomyosarcomas account for up to 21% of vascular leiomyosarcomas, with 56% of arterial leiomyosarcomas occurring in the pulmonary artery. While isolated cases of primary pulmonary artery leiomyosarcoma document survival up to 36 months after treatment, these uncommon, aggressive tumors are highly lethal, with 1-year survival estimated at 20% from the onset of symptoms. We discuss a rare case of a pulmonary artery leiomyosarcoma that was originally diagnosed as a pulmonary embolism (PE). A 72-year-old Caucasian female was initially diagnosed with 'saddle pulmonary embolism' based on computerized tomographic angiography of the chest 2 months prior to admission and placed on anticoagulation. Dyspnea escalated, and serial computed tomography scans showed cardiomegaly with pulmonary emboli involving the right and left main pulmonary arteries with extension into the right and left upper and lower lobe branches. An echocardiogram on admission showed severe pulmonary hypertension with a pulmonary artery pressure of 82.9 mm Hg, and a severely enlarged right ventricle. Respiratory distress and multiorgan failure developed and, unfortunately, the patient expired. Autopsy showed a lobulated, yellow mass throughout the main pulmonary arteries measuring 13 cm in diameter. The mass extended into the parenchyma of the right upper lobe. On microscopy, the mass was consistent with a high-grade primary pulmonary artery leiomyosarcoma. Median survival of patients with primary pulmonary artery leiomyosarcoma without surgery is one and a half months, and mortality is usually due to right-sided heart failure. Pulmonary artery leiomyosarcoma is a rare but highly lethal disease commonly mistaken for PE. Thus, we recommend clinicians to suspect this malignancy when anticoagulation fails to relieve initial symptoms. In conclusion, early detection and suspicion of pulmonary artery leiomyosarcoma should be considered in patients refractory to anticoagulation, prompting initiation of early intervention.

Dual-energy CT-based iodine quantification for differentiating pulmonary artery sarcoma from pulmonary thromboembolism: a pilot study

OBJECTIVES

The purpose of this study was to determine whether dual-energy computed tomography (DECT) angiography could differentiate pulmonary thromboembolism (PTE) from pulmonary artery sarcoma (PAS).

METHODS

We prospectively enrolled 19 patients that had a filling defect in the main pulmonary artery on DECT. Six patients who had PAS and underwent DECT were retrospectively enrolled for comparison. Pathological results or follow-up CT after anticoagulation therapy were used to make the final diagnosis. Two investigators measured the following parameters at the filling defect in the main pulmonary artery: CT attenuation density [Hounsfield units (HU)], iodine-related HU (IHU) and iodine concentration (IC, mg/ml).

RESULTS

From a total of 25 patients (M:F = 10:15; mean age, 65 years old), 19 were categorised into the PTE group and six were categorised into the PAS group. The mean HU values were not significantly different between the PTE and PAS groups (45.5 ± 15.9 vs 47.1 ± 9.2 HU; P = 0.776). However, the mean IHU and IC values of the lesions were significantly different between the PTE and PAS groups (10.6 ± 7.2 vs 27.9 ± 9.1 HU; P = 0.004, and 0.61 ± 0.39 vs 1.49 ± 0.57; P = 0.001).

CONCLUSIONS

DECT angiography using a quantitative analytic methodology can be used to differentiate PTE and PAS.

KEY POINTS

• DECT can be useful for differentiation of PAS and PTE. • With quantitative analysis, DECT offers tissue characterisation by detecting lesion parameter increases. • The patients without predisposing factors for PTE can be candidates for DECT.