Misdiagnosed Primary Pulmonary Synovial Sarcoma: A Case Report Emphasizing Diagnostic Pitfalls and the Crucial Role of Molecular Testing.

Primary pulmonary synovial sarcoma (PPSS) is an extremely rare malignancy that presents diagnostic challenges due to its overlapping clinical features with other lung diseases. We present the case of a 53-year-old woman with a history of bronchial artery malformation and right lung organizing pneumonia, who experienced an eight-month history of intermittent cough and sputum. Despite multiple imaging studies and biopsies at different hospitals, a definitive diagnosis was not reached until a CT scan of the chest revealed an enlarged mass in the right lower lobe. The patient underwent video-assisted thoracoscopic surgery, where intraoperative findings and pathological examination confirmed a spindle cell tumor. Immunohistochemistry and next-generation sequencing then identified the presence of a gene fusion, confirming the diagnosis of PPSS. This case illustrates how PPSS can mimic other malignancies or infections and underscores the importance of advanced diagnostic techniques, such as immunohistochemistry and molecular testing, in facilitating an accurate diagnosis.