Pulmonary artery intimal sarcoma. Problems in the differential diagnosis

Pulmonary artery sarcomas (PAS) are rare malignant tumours that originate from the intimal layer of the pulmonary artery, occur in middle age and have a poor prognosis. In planning appropriate treatment, malignant disease should be suspected whenever there are specific clinical and radiological manifestations, in order to establish the differential diagnosis with acute pulmonary embolism or chronic thromboembolic pulmonary hypertension, with which this malignancy is most commonly confused.

Between 2008 and 2012, we managed four adult patients with a nonspecific clinical presentation who, at the conclusion of the diagnostic process, were found to be affected by PAS. Because of the initial suspicion of pulmonary embolism, all patients underwent chest radiograph, lung perfusion scintigraphy, trans-oesophageal echocardiography, and computed tomography (CT) angiography of the chest. Then, because of the peculiar CT findings and lack of response to anticoagulation therapy, a clinical suspicion of PAS was considered and all patients underwent positron-emission tomography (PET)-CT, and one patient also magnetic resonance imaging (MRI) of the chest. Subsequently, all patients underwent thromboendoarterectomy with histological investigation of the surgical specimen, which confirmed the clinical and radiological suspicion of PAS.

CT is the technique that enabled the first step in the differential diagnosis between PAS and pulmonary embolism. The CT characteristics suggestive of PAS included the particular filling defect occupying the entire lumen of the pulmonary trunk with increase in diameter of the involved vessel and patchy and delayed contrast enhancement at CT angiography, more evident in the venous phase. PET-CT was used to differentiate between PAS and pulmonary embolism on the basis of the intensity of increased radiopharmaceutical uptake. MRI was used in one case of equivocal results on PET-CT, to improve tissue characterisation of the lesions and differentiation between the thrombotic and neoplastic components.

The radiologist is usually the first to raise a suspicion of PAS in patients with severe dyspnoea and filling defect in the pulmonary artery, unresponsive to anticoagulation therapy. Combining CT and PET-CT proved to be extremely useful in assessing patients with suspected PAS. Early diagnosis with the help of integrated imaging remains today the main direction to pursue in order to obtain improvements in prognosis.