Pulmonary pleomorphic carcinoma associated with cystic airspace and recurrent spontaneous pneumothorax: A case report.

Pulmonary pleomorphic carcinoma (PPC), classified as the predominant subtype of pulmonary sarcomatoid carcinoma under the current World Health Organization (WHO) criteria, accounts for 0.1-0.4% of all non-small cell lung carcinoma cases and typically manifests radiologically as solid masses with peripheral infiltration. In the present report, a novel clinicopathological manifestation of PPC presenting as a primary solitary cystic airspace with recurrent spontaneous pneumothorax (SP), challenging conventional diagnostic paradigms, is described. A 66-year-old man with recurrent SP was initially misdiagnosed with pulmonary bullae based on the peripheral cystic airspaces observed on computed tomography. Persistent air leakage prompted video-assisted thoracoscopic wedge resection, which revealed biphasic histology: Malignant spindle cell proliferations (vimentin-positive) mixed with conventional adenocarcinoma components (transcription termination factor 1-positive/napsin A-positive), consistent with the WHO 2021 diagnostic criteria for PPC. The patient reached sustained remission without adjuvant therapy, and disease-free survival was maintained for 29 months. The present case highlights three critical implications: First, primary cystic airspaces represent a rare but clinically significant radiological phenotype of PPC that mimic benign bullous lesions, particularly when obscured by pneumothorax; second, recurrent SP may serve as the initial manifestation of occult pulmonary malignancy, necessitating rigorous evaluation of cystic lung lesions; third, early surgical intervention offers dual diagnostic and therapeutic value, even in patients with compromised pulmonary function. These findings expand the recognized spectrum of the imaging heterogeneity of PPC and underscore the need for heightened clinical suspicion of cystic lung cancer in high-risk populations.