Correct!
3. Pulmonary artery sarcoma
is an intraluminal filling defect that is heterogeneous, possibly enhancing, in the left pulmonary artery, which is the same side as the two lung nodules, and this filling defect is highly FDG-avid. The morphology of this lesion is consistent with a lesion arising from the left pulmonary artery itself, and is not typical for thromboembolic disease. Occasionally thromboembolic disease can show FDG tracer uptake, but usually the uptake is far less intense than seen here. In the context of a lung biopsy showing sarcoma, the findings are diagnostic of primary pulmonary artery sarcoma. There are numerous potential causes of non-thrombotic pulmonary artery emboli, including hydatid disease, particulates, foreign bodies [such as wires, filter fragments, catheters, etc.], methyl methacrylate, and other etiologies, but these conditions usually have characteristic appearances that suggest the proper diagnosis, and would not be expected to be FDG-avid For example, wires and catheters have a tubular appearance, the former appearing metallic, the latter plastic and hyperattenuating. Hydatid embolism may appear as low attenuation, cystic expansion of the pulmonary artery, perhaps accompanied by cardiac cysts as well. The lesion in this circumstance shows soft tissue attenuation and appears quite irregular. Septic embolization often shows no pulmonary arterial filling defects and is associated with multiple bilateral lung nodules with poorly defined margins that undergo cavitation. When septic pulmonary embolization is associated with central pulmonary arterial filling defects, these defects have an appearance identical to thromboembolic disease. Pulmonary arterial dissection is a rare condition that is most commonly encountered in the setting of pulmonary hypertension, on CT appearing a long, typically single, linear filling defect, representing the intimo-medial flap, within the lumen of the pulmonary artery. Pulmonary artery dissection would not show focal, mass-lie tracer accumulation at FDG-PET scan.
Diagnosis: Pulmonary artery sarcoma
Post-script. The patient underwent left pneumonectomy without complication. Shortly following his recovery from surgery, repeat chest CT (Figure 6) showed expected post-pneumonectomy findings, without tumor recurrence.
Figure 6: Axial enhanced thoracic CT through the level of the main and right pulmonary artery 3 months following left pneumonectomy shows a normal post-operative appearance of the left pneumonectomy space.
However, 8 months later, repeat chest CT (Figure 7) showed recurrence of the tumor.
Figure 7. Axial enhanced thoracic CT through the level of the main and right pulmonary artery 10 months following left pneumonectomy shows a new soft tissue filling defect within the main and proximal right pulmonary artery (arrow), representing tumor recurrence.
References