A80-4-23 When Rare Becomes Real: Diagnostic Challenges and Utility of a Multidisciplinary Team-based Decision in a Case of Primary Pulmonary Synovial Sarcoma

Abstract Primary pulmonary synovial sarcoma is an exceptionally rare malignancy, accounting to only 0.5% of all primary lung malignancies. It is associated with an aggressive growth and carries a poor prognosis, with a reported 5-year survival rate of 30-50%. Patients present with non-specific respiratory symptoms and imaging findings typically reveal an ill-defined pulmonary mass without distinctive radiologic features. Histopathologic evaluation is also challenging due to its spindle cell morphology which can resemble benign granulomatous lesions or other malignant tumors, necessitating immunohistochemical (IHC) profiling and fusion gene testing (SSX1 or SSX2) for definitive diagnosis. This report describes a case of primary pulmonary synovial sarcoma that is diagnosed promptly through the collaborative approach of a multidisciplinary team discussion. A 21-year-old male presented with a six-week history of cough and hemoptysis. Initial chest CT revealed a 2.2 cm endobronchial mass in the left mainstem bronchus, resulting in complete atelectasis of the left lung. Bronchoscopy confirmed the obstructing lesion; however, biopsy only showed reactive epithelial cells and the patient was referred to our institution three months later. Subsequent PET-CT demonstrated interval growth of the mass to 8.2 cm in maximal diameter without evidence of hypermetabolic metastases. A CT-guided biopsy was performed, revealing a spindle cell lesion prompting further evaluation through immunohistochemical studies and SS18 fluorescence in situ hybridization (FISH) testing. IHCs demonstrated weak to moderately positive pancytokeratin stain, equivocal desmin stain, and negative results for ALK, SMA, CD34 and S100. SS18 FISH testing also showed a negative result. Although next-generation sequencing was recommended for further molecular characterization, it was not performed due to financial and logistical limitations. Based on these findings and through the discussion of a multidisciplinary team, a diagnosis of low-grade primary pulmonary synovial sarcoma was made. The patient was then initiated on neoadjuvant chemotherapy with doxorubicin, ifosfamide, and mesna, with plans for a sleeve pneumonectomy. The diagnosis of primary pulmonary synovial sarcoma poses significant challenges and delays, from initial clinical presentation to the interpretation of imaging and histopathologic findings. Early referral to a specialized lung center, coupled with a multidisciplinary team-based approach, is essential to facilitate timely diagnosis, expedite clinical decision-making, and potentially improve patient outcomes. This abstract is funded by: None