Imaging description

Pulmonary artery (PA) sarcoma is a rare tumor that is difficult to diagnose due to clinical presentation and imaging appearance that mimic pulmonary embolism. On contrast-enhanced CT, pulmonary artery sarcoma can appear nearly identical to a pulmonary embolism, usually appearing as a smooth, lowattenuation intraluminal filling defect (Figure 46.1). Clinically, the absence of risk factors for thrombus formation, progressive worsening of symptoms, and persistence of the pulmonary artery filling defect despite anticoagulation therapy should raise suspicion for pulmonary artery sarcoma (Figure 46.2). CT features that may help distinguish sarcoma from embolus include involvement of the main and proximal pulmonary artery branches, filling and expansion of the entire luminal diameter, and extravascular extension of soft tissue into the adjacent lung parenchyma. Contrast enhancement, when identified, is usually heterogenous and will suggest the diagnosis (Figure 46.1). However, enhancement may be difficult to appreciate on CT examinations performed with pulmonary embolism protocol due to early phase of acquisition. Delayed venous phase images or enhanced chest MRI with dynamic post-contrast imaging can be used to confirmthe presence of enhancement. PA sarcomas will show increased metabolic activity on FDG-PET examinations, which can be helpful in difficult cases.

Importance

Incorrect interpretation of a PA sarcoma as a pulmonary embolism will lead to a delay in diagnosis and delayed institution of proper treatment.

Typical clinical scenario

Pulmonary artery sarcomas are rare tumors, with only 250 cases reported in the literature to date. Patients are typically middle aged and usually present with symptoms of dyspnea.

Differential diagnosis

The primary differential diagnosis is bland thromboembolism. Metastatic tumor emboli from a non-lung primary can also present with enhancing, expansile pulmonary artery filling defects and should also be considered.