Imaging Findings of Primary Pulmonary Synovial Sarcoma with Secondary Distant Metastases: A Case Report

Background: Synovial sarcoma (SS) accounting for 6%-10% of primary soft tissue malignancies mainly occurs in deep soft tissue adjacent to joints of the limbs. Primary pulmonary SS (PPSS) is rare and has a poor prognosis. Cases of secondary distant metastases of PPSS occur rarely and there is a lack of corresponding imaging reports. We summarized the imaging findings of PPSS with multiple metastases confirmed by surgery and pathology, and shared valuable information on PPSS.

Case Summary: A 43-year-old female patient had a solid space occupying lesion in the right upper lobe of the lung. The results of a hemogram, erythrocyte sedimentation rate (ESR) and tumor markers were all within the normal range, tuberculin skin test (5 TU PPD) was negative (-). Chest computed tomography examination showed similar round soft tissue density in the posterior segment of the right upper lobe. Thoracoscopic-assisted wedge resection of the right upper lobe of the lung, right upper lobe resection and lymph node dissection were performed. Nine months after surgery, ultrasound examination showed multiple metastases on the chest wall and kidney.

Conclusion: PPSS is a rare malignant lung tumor with strong invasiveness, early distant metastasis and poor prognosis. There are very few imaging reports. PPSS is often manifested as irregular tumor and calcification, and the metastases have extremely low echo on ultrasonography. Contrast-enhanced ultrasound indicates that the arterial phase of tumor metastases shows rapid centripetal high enhancement, manifested as "fast forward and fast regression".