Solitary fibrous tumor of the lung: diagnostic challenges and surgical management.

Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms that typically arise from the pleura but may occur in various extrathoracic sites. Primary intraparenchymal pulmonary SFTs without pleural attachment are exceptionally uncommon and often pose diagnostic and therapeutic challenges. We report the case of a middle-aged female patient presenting with progressive dyspnea and a large mass in the left lower lobe on imaging. Computed tomography revealed a well-circumscribed, hypervascular mass occupying the left lower lobe. Bronchoscopic and percutaneous biopsies were nondiagnostic, and surgical resection was pursued. Intraoperatively, the tumor was found to arise from the lung parenchyma without pleural involvement. Histopathological examination demonstrated a spindle-cell neoplasm with the typical "patternless pattern," and immunohistochemistry confirmed nuclear STAT6 positivity, establishing the diagnosis of SFT. The postoperative course was uneventful apart from a transient pulmonary embolism, which was successfully treated. The patient was discharged in good condition and is under regular radiologic surveillance. SFTs of the lung are rare and often mimic more common pulmonary tumors radiologically. Histologic confirmation with STAT6 immunohistochemistry is crucial for accurate diagnosis. Complete surgical excision remains the mainstay of treatment. Given the risk of late recurrence-especially in large tumors-long-term imaging follow-up is mandatory. This case highlights the importance of considering SFT in the differential diagnosis of large pulmonary masses, the critical role of STAT6-based histopathologic confirmation, and the necessity for prolonged surveillance even after complete resection.