Joint Program in Nuclear Medicine

PET Imaging of Pulmonary Artery Sarcoma

Hossein Jadvar, MD, PhD
J. Anthony Parker, MD, PhD

September 29, 1998

Presentation

A 58 year old female was admitted to the hospital for further evaluation of cough, weight loss, and hemoptysis. Previous work-up revealed a right hilar mass. A bone scan and a head MRI were negative. A lung scan showed a ventilation perfusion mismatch in the right lower lobe, and the patient was anticoagulated. On admission the physical examination was normal except for tachypnea (respiratory rate of 23/min.) and tachycardia (heart rate of 95/min.). An MRI of the chest and a fluorodexoyglucose (FDG) PET scan were obtained.

Imaging Technique

Lung scan: Ventilation scan in the posterior projection was performed with Xe-133 gass followed by an 8 view perfusion scan.
Chest MRI: Axial T1, sagittal T1 and coronal 3D FISP images were obtained post-gadolinium injection.
FDG PET: Coincidence imaging was performed 1.5 hours after intravenous injection of F-18 labelled FDG in the fasting state.

Imaging Findings

Lung scan: The perfusion scan shows decreased perfusion in the right lung particularly the right lower lobe (arrows show defect). Single breath image from the ventilation scan (left) shows normal ventilation in the region of abnormal perfusion (right). Arrows show the area of mismatch.
FDG PET and MRI: Axial images show a hypermetabolic lesion in the right hilum (FDG PET on left) and an ill-defined right hilar mass abutting right pulmonary artery at its bifurcation (MRI on right). Arrows on the axial images show the mass. Coronal images show that the hypermetabolic region (FDG PET on left) is associated intraluminal filling defect (MRI on right). Arrows on the coronal images show the mass. Not shown were peripheral embolic disease, and scattered 1 cm lymph nodes.

Differential Diagnosis

The most common cause of a ventilation perfusion mismatch is pulmonary embolization; however, any cause of pulmonary artery obstruction can produce the same findings. The differential diagnosis also includes bronchogenic carcinoma, lymphoma, metastatic disease, sarcoma, aneurysm, sarcoid, and fungal or granulomatous infection.
However, the hypermetabolic nature of the right hilar mass makes pulmonary embolization unlikely.

Diagnosis

The patient underwent right thoracotomy and right pneumonectomy. The surgical specimen revealed a pulmonary artery sarcoma.

Discussion

Background:

Pulmonary artery sarcoma is a rare neoplasm that arises from the central pulmonary arteries. The most common site for metastases is the lung. It is more common in females (2:1 female:male ratio) in the age range 22 to 81 years (1). The signs and symptoms include systolic murmur, cyanosis, dyspnea, chest pain, cough, hemoptysis, and syncope. The clinical presentation and radiologic features may mimic pulmonary embolism due to pulmonary arterial flow reduction (2). Some patients are therefore treated with anticoagulation which may not result in the resolution of symptoms. When tumor is suspected, surgery can be both diagnostic and therapeutic. The prognosis, however, is very poor with a mean survival of about one year after the onset of symptoms (3).

Radiologic Imaging:

The radiographic features include decreased pulmonary vascular markings, central pulmonary artery enlargement, or a hilar mass (4). CT or MRI may show expansion of the pulmonary artery by a soft tissue mass which may be associated with regional or global ipsilateral lung oligemia, pulmonary infarction, or peripheral pulmonary nodules (5, 6). One case report also demonstrated the neoplasm as an intravascular echogenic mass with right ventricular strain on 2D-echocardiography (7).

Scintigraphic Imaging:

Lung scan may be performed in these patients due to similarity of the clinical presentation to pulmonary embolism. Mismatched diminished perfusion abnormalities on the lung scan may suggest high likelihood ratio for pulmonary embolism. In one case report, gallium-67 scan was useful in identifying the tumor (8).

FDG PET Imaging:

There are no previous reports of the use of FDG PET imaging, either with a dedicated PET camera or a gamma camera with coincidence circuitry, for the evaluation of pulmonary artery sarcoma. In our patient, the tumor was clearly hypermetabolic which was highly suspicious for malignancy. Tumor was confirmed by surgical pathology.

Conclusion:

FDG PET is useful for the evaluation of patients with a hilar mass who may have initially been unsuccessfully treated for pulmonary embolism. Malignancy including pulmonary artery sarcoma should be considered if the mass is hypermetabolic.

References

Baker PB, et al: Pulmonary artery sarcoma. Arch Pathol Lab Med 1985; 109:35-39.
Delany SG, et al: Pulmonary artery sarcoma mimicking pulmonary embolism. Chest 1993; 103(5): 1631-1633.
Britton PD. Primary pulmonary artery sarcoma-A report of two cases, with special emphasis on the diagnostic problems. Clin Radiol 1990; 41: 92-94.
Moffat RE, et al. Roentgen considerations in primary pulmonary artery sarcoma. Radiology 1972; 104: 283-288.
Fitzgerald PM. Primary sarcoma of the pulmonary trunk: CT findings. J Comput Assist Tomogr 1983; 7: 521-523.
Smith et al: MR and CT findings in pulmonary artery sarcoma. J Comput Assist Tomogr 1989; 13(5): 906-909.
Wright EC, et al: Primary pulmonary artery sarcoma diagnosed noninvasively by two-dimensional echocardiography. Circulation 1983; 67(2): 459-462.
Myerson PJ, et al: Gallium imaging in pulmonary artery sarcoma mimicking pulmonary embolism: case report. J Nucl Med 1976; 17(10): 893-895.

Click here to go to Joint Program in Nuclear Medicine home page and Copyright notice.

J. Anthony Parker, MD PhD, Tony_Parker@bidmc.harvard.edu