Squamous cell carcinoma presenting as a solitary growing cyst in lung: a diagnostic pitfall in daily clinical practice.

Gradually growing cystic lesion of the lung is commonly encountered in daily clinical practice. Thin-walled cavitary lung cancer is a rare entity; however, it could be a pitfall in the diagnosis of such radiographically benign-looking lesions, especially without an obvious solid, nodular, or tumorous appearance in the lesion. We herein report a rare case of lung cancer successfully treated by surgical resection that appeared as a gradually growing cystic lesion mimicking benign emphysematous disease, with a review of the literature. A 68-year-old man with a 24-year history of hypothyroidism presented with an abnormal cystic shadow in the left lung on routine chest X-ray. Twelve months later, occasional bloody sputa had started and was gradually getting worse. The patient was then referred to our department for surgical intervention. He received clarithromycin by daily oral administration, and the bloody sputa soon disappeared. However, a malignancy was still suspected because the wall was slightly thickened unevenly in comparison with the previous chest X-ray and computed tomography findings. Thus we performed a left lower lobectomy followed by mediastinal dissection because a squamous cell carcinoma was diagnosed by intraoperative frozen section. The patient postoperatively received 4 courses of paclitaxel-carboplatin therapy. Twelve months after surgery, he survives without recurrence.