Pulmonary artery sarcomas are very rare tumors, with a reported incidence of 0.001 to 0.003% and a total of 148 cases reported as of 2001. Mortality is virtually 100%. However, there is reported survival when the diagnosis is established early. The diagnosis is often difficult and delayed because the clinical presentation and radiographic findings can be indistinguishable from thromboembolic disease and tumor emboli. Consequently, pulmonary artery sarcomas are underrecognized and underreported. However, there are several features that may help differentiate between thromboembolic disease and primary tumors of the pulmonary artery. Patients with pulmonary artery tumors will generally have a gradual, progressive, subacute to chronic course characterized by weight loss, fatigue, weakness, and fever. These features are generally absent from those in patients with thromboembolic disease. Normal findings on venography or Doppler ultrasound of the lower extremities and deep pelvic veins can help exclude venous thrombosis as an underlying cause. Serial ventilation/perfusion scanning demonstrate static or progressive defects, as opposed to changing perfusion defects seen more commonly in treated patients with thromboembolic disease. Pulmonary angiography may reveal a smooth gradual tapering of the pulmonary artery and pruning of the distal vessels. This is more suggestive of tumor and less likely evident in thromboembolism. A characteristic oscillating motion that simulates a tumor on a pedicle is heralded as pathognomonic for tumor and is unlikely to be present in thromboembolism. Once a diagnosis is established, mean survival is only 1.5 months without surgical intervention; therefore, early diagnosis is essential in treatment.