Recurrent bilateral spontaneous pneumothorax secondary to lung adenocarcinoma with epidermal growth factor receptor mutation

A 42‐year‐old female patient was admitted for recurrent bilateral spontaneous pneumothorax. High resolution computed tomography showed bilateral pneumothorax and numerous round and oval, thin‐walled lung cysts. Microscopically, each small cyst was composed of distended subpleural alveolar spaces. Tumor cells, characteristic of acinar adenocarcinoma, obstructed and narrowed the terminal bronchioles. There was no tumor necrosis or mucin production. This suggested check‐valve as a possible mechanism of the thin‐walled cysts and pneumothorax. Genetic analysis suggested that the tumors were positive for epidermal growth factor receptor mutation L858R in exon 21. Bilateral spontaneous pneumothorax and thin‐walled cysts in association with lung cancer is rarely reported and may be confused with cystic benign lung lesions.