Imaging Findings in Pulmonary Tumour Embolism from Chondrosarcoma- A Case Report and Review of Literature

A 73yr old male patient had presented to the department of pulmonology with complaints of progressively increasing shortness of breath for 3 weeks. Echocardiography revealed pulmonary hypertension and right heart overload pattern. Chest radiograph showed ill-defined nodular opacities in bilateral lung parenchyma. CT pulmonary angiogram with contrast demonstrated filling defects within the pulmonary artery divisions extending into the lobar and segmental, subsegmental branches with a beaded pattern of dilatation. Enhancement was seen post contrast within the filling defects. In view of the classical imaging and history of radiotherapy for chondrosarcoma of the pelvis three years ago, diagnosis of pulmonary tumour embolism was made. We present the CT imaging findings in pulmonary tumour embolism in this patient with review of literature

Pulmonary thrombo-embolism is not an uncommon occurrence in patients with malignancy due to predisposition caused by the hypercoagulable state. But embolism from non- thrombotic substances can also present with similar clinical symptoms [1,2]. Embolism of the tumour cells into the pulmonary circulation is an under-recognised clinical complication, which can present with either acute or subacute onset of shortness of breath or progressive pulmonary hypertension depending on the size of the embolic material [3-5]. In this case report, we present imaging findings of a patient diagnosed with pulmonary tumour thromboembolism who was previously treated for chondrosarcoma of the pelvis.

A 72-year-old male was brought to the pulmonology department with complaints of progressively increasing shortness of breath (SOB) in the three weeks with worsening of SOB for 3 days. There was also history of productive cough and chest pain for one week. The patient’s blood pressure was 90 / 50 mm Hg at presentation and the oxygen saturation was 92% on room air.

There was prior history of biopsy proven chondrosarcoma of the right acetabulum in the patient 3 years ago. PET/CT study done (at an outside hospital) at the time of diagnosis had demonstrated hypermetabolic right acetabular mass with an exophytic soft tissue component. The patient was unwilling to undergo amputation and was treated with 4 cycles of radiotherapy, after which he had refused medical treatment until the present complaints.

Emergency bedside echocardiography demonstrated dilated right atrium, right ventricle, severe pulmonary arterial hypertension and severe tricuspid regurgitation. Left ventricular systolic function was found to be normal. The IVC was dilated, measuring 2 cm.

Troponin I value were elevated at 596.1 ng/L (normal biological reference: less than 19ng/L)

Plasma D-Dimer was elevated at 3256 ng/L (normal biological reference: positive if > 500 ng/L). 

Chest radiograph at presentation (Fig 1) showed multiple ill-defined nodular parenchymal opacities bilaterally. Possibility of pulmonary metastases from sarcoma was considered on the radiograph due to prior history of treatment for chondrosarcoma.

Figure 1: Chest radiograph PA view shows multiple bilateral ill-defined parenchymal nodules

The patient was put on 2 L oxygen with nasal prongs and nor-adrenaline drip and underwent CT pulmonary angiogram including HRCT of the lungs. HRCT images showed bilateral tortuous tubular densities extending up to the lung periphery, seen in contiguity with the pulmonary arterial divisions (Fig 2). There were no discrete intraparenchymal pulmonary nodules.

Figure 2: HRCT chest shows tubular beaded densities along the course of pulmonary arteries bilaterally.

Dynamic multiphase CT pulmonary angiogram with free breathing was performed due to tachycardia (heart rate of 105 bpm) and inability of the patient to hold breath. CT pulmonary angiogram showed intraluminal enhancing soft tissue within the lower lobar right and left pulmonary artery causing complete occlusion (Fig 3, Fig 4a, b). Filling defect was also noted within the right atrium anteriorly (Fig 3).

Figure 3: Axial post contrast image shows filling defect in the left lower lobe pulmonary artery (long blue arrow), in the right lower lobe pulmonary artery (short blue arrow) and in a peripheral branch of lingula (yellow Asterix). Also seen is a filling defect in the right atrium (yellow arrow)

Figure 4: Axial plain image (a) and the corresponding section on the postcontrast study (b) demonstrate enhancement within the left lower lobe pulmonary artery filling defect. HU value within the yellow circled area- precontrast attenuation of 30 HU in (a) and postcontrast attenuation of 91 HU (b)

Several such enhancing filling defects were seen diffusely involving multiple lobar and segmental divisions of the pulmonary artery bilaterally, with some extending up to the periphery (Fig 5a, b). The involved branches were dilated and tortuous with beaded appearance. Based on the imaging findings and history of chondrosarcoma, a diagnosis of pulmonary arterial tumour embolism was made. 

Figure 5: Axial (a) and coronal (b) postcontrast MIP images demonstrate multifocal filling defects within the divisions of pulmonary artery bilaterally with dilated beaded appearance

Non-thrombotic pulmonary embolism (NTPE) has complex and varied pathogenesis when compared to pulmonary thromboembolism. It involves embolization, to the pulmonary circulation, of different types of cells such as adipocytes, haematopoietic cells, trophoblastic cells, tumour cells, amniotic fluid, bacteria, fungal, foreign material, or gas [2,6]. The pathogenesis and presentation of non-thrombotic emboli is not merely mechanical, but more complex, as they may be characterized by endothelial and parenchymal injury with an inflammatory reaction both in the systemic and pulmonary circulation [2,6,7].

Embolism of tumour cells from a distant primary neoplasm to the pulmonary vasculature was first described in 1897 [7,8]. Pulmonary tumour embolism can be macro embolism where there is occlusion of the larger proximal vessels by a large amount of tumour material or micro-embolism involving the small arterioles and alveolar septal capillaries [2,7]. Tumour embolism is different from pulmonary metastasis as the tumour cells in embolism are confined to within the pulmonary vasculature and rarely invade the pulmonary parenchyma [5]. Different post-mortem studies have estimated the incidence of tumour embolism in patients with malignancy between 2.4 to 26% [7,9,10]. Renal cell, adrenocortical, stomach, breast, hepatocellular carcinomas, choriocarcinoma, and sarcomas are the most common sources of pulmonary tumour embolism [9,11]. An evaluation of tumour embolism in cadavers of patients with malignancy revealed that 13% of tumour emboli were from sarcomas [12].

Clinical presentation usually involves acute to subacute dyspnoea, often progressing over days to weeks, associated with cough, haemoptysis, and chest pain. Physical examination and echocardiography often reveal pulmonary hypertension and signs of right heart overload, like pulmonary thromboembolism [1,5,7]. The clinical presentation in our patient was very similar to that mentioned in literature. In addition, the elevated D-Dimer value and troponin I values had prompted the clinical team to request for a CT pulmonary angiogram to look for pulmonary thromboembolism.

In most cases, tumour embolism can be clinically and radiologically indistinguishable from thromboembolism. Hence a high index of clinical and radiological suspicion together with knowledge of imaging findings is essential to make the diagnosis [5]. Imaging findings on CT depend upon the size of the vessels affected. CT angiogram/contrast CT findings specific for tumour macro-embolism include multifocal dilated and beaded peripheral arteries, contrast enhancement of intravascular filling defects and F18-fluorodeoxyglucose (FDG) avidity on PET/CT [5,7,11,13]. Additionally, bilateral peripheral wedge-shaped opacities, suggestive of pulmonary infarcts, have also been reported [7]. When the tumour emboli involve the small centrilobular arterioles, tree-in-bud pattern of nodules is the imaging presentation [5]. Evidence pertaining to imaging in tumour embolism in the setting of sarcoma is limited to a few case reports and case series [13,15]. The clinical presentation and the classic imaging findings of enhancing macro emboli in the larger pulmonary arterial branches together with the beaded dilatation of the peripheral branches clinched the diagnosis of pulmonary tumour embolism in our patient who had a history of chondrosarcoma. The additional finding of right atrial filling defect suggested the presence of tumour embolus in transit, as described in literature [16].

Pulmonary tumour embolism should be suspected in patients with known malignancy presenting with subacute dyspnoea and signs of pulmonary hypertension. An awareness of the classic imaging findings of enhancing filling defects within the pulmonary artery with beaded dilatation of the arterial branches is essential to differentiate tumour embolism from thromboembolism.