Diagnostic Dilemma of Rounded Atelectasis in the Left Lower Lobe Showing High Uptake of 18F-Fluorodeoxyglucose: A Surgical Conundrum

Differentiating rounded atelectasis from lung cancer can be challenging. Rounded atelectasis has a low-to-moderate maximum standardized uptake value of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG); however, some cases show high uptake, meaning that radiology-based diagnoses may not always be accurate. Herein, we report a rare surgical case of a patient with rounded atelectasis exhibiting considerable ¹⁸F-FDG uptake. A 55-year-old man with a 37-pack-year smoking history was referred to our hospital for further investigation of an abnormal shadow in the left lower lung field. Chest computed tomography (CT) revealed a 45-mm solid tumor with bronchovascular convergence forming a "comet tail" sign in the left lower lung lobe. Positron emission tomography/CT with ¹⁸F-FDG showed increased uptake within a 30-mm region of the subpleural mass (SUVmax: 6.5). These findings necessitated a differential diagnosis to distinguish rounded atelectasis from lung cancer. The patient underwent video-assisted thoracoscopic left lower lung lobectomy with hilar lymph node dissection. Pathological investigation revealed granulomatous pleuritis and pneumonitis with no evidence of malignancy, consistent with rounded atelectasis. The patient had an uneventful postoperative course and was discharged six days after surgery. During a two-year follow-up period, no health-related issues, including lung cancer development, have been observed. This rare case highlights the importance of a thorough investigation to exclude the possibility of lung cancer before confirming a diagnosis of rounded atelectasis in patients with pulmonary lesions exhibiting high ¹⁸F-FDG accumulation.