Pulmonary artery sarcoma
Primary malignant tumors of the pulmonary arteries are very rare with an incidence of 0.001–0.03%. It usually presents in adults, with median age of presentation of 45 years. It is more prevalent in females.
The patient usually presents with a long and gradual onset pulmonary artery occlusion and right sided cardiac failure, features almost indistinguishable from pulmonary thromboembolic disease.
Most pulmonary artery sarcomas are believed to originate from pleuripotent intimal cells, and they are called intimal sarcomas. The latter are typically poorly differentiated malignant mesenchymal tumors. On the other hand, it is thought that leiomyosarcomas of the pulmonary artery arise from the vascular media, and the term mural sarcoma has been proposed. Nevertheless, the distinction can generally only be made microscopically, since grossly, both types of the tumor form a mass in the lumen and grow along the involved vessel.
Pulmonary artery sarcoma is a low-attenuation lesion, and there is vascular distention when the tumor fills the lumen. Since these tumors are metabolically active, they show more FDG positivity on PET-CT scans than do thrombi.
In an attempt to distinguish pulmonary artery sarcoma from pulmonary embolic disease, Yi et al. reported that CT findings favoring the diagnosis of pulmonary artery sarcoma include :
- a low-attenuation filling defect occupying the entire luminal diameter of the proximal or main pulmonary artery
- expansion of the involved arteries
- extraluminal tumor extension
MRI is highly specific in recognizing pulmonary artery sarcoma since the tumor enhances post-gadolinium contrast more than bland thrombus.
FDG avidity may be able to differentiate pulmonary artery sarcomas from thrombus. A small case series reports SUVmax values of 7.6 ± 2 (n = 3) for pulmonary artery sarcoma compared to 2.3 ± 0.4 (n = 10) for thrombus . However, FDG PET can not rule out low grade sarcomas which are often mildly FDG avid.
Treatment and prognosis
Pulmonary artery sarcoma is highly malignant tumor, with a mean survival of 12-18 months from time of presentation.
Surgical resection is the mainstay treatment option for patients with intimal sarcoma involving the pulmonary artery. However, treatment may involve one or several interventions including chemotherapy, radiation therapy, and/or surgery. However, even with multimodality treatment including surgery, the prognosis for patients with pulmonary artery sarcoma is dismal.