The Contribution of Radial Endobronchial Ultrasound (EBUS) in the Diagnosis of Pulmonary Cystic Lesions

Neoplasms arising within pulmonary cystic airspaces are rare and diagnostically challenging entities that frequently lead to delayed recognition and advanced disease at diagnosis. We report the case of a 61-year-old smoker who presented with significant weight loss and two cystic pulmonary lesions on chest computed tomography (CT). An initial CT-guided transthoracic biopsy was non-diagnostic, and the patient subsequently underwent imaging surveillance. Follow-up CT demonstrated interval growth, progressive wall thickening, and spiculated margins, while ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) showed intense metabolic uptake, raising a strong suspicion for malignancy. Subsequent bronchoscopy with radial endobronchial ultrasound (r-EBUS) enabled real-time localization and transbronchial sampling of the lesion, confirming pulmonary adenocarcinoma. This case highlights the importance of maintaining a high index of suspicion for malignancy in cystic lung lesions, particularly in high-risk patients, and underscores the diagnostic value of r-EBUS as a safe, minimally invasive approach when conventional biopsy techniques are non-diagnostic.