A case of localized middle lobe pulmonary alveolar proteinosis that was difficult to distinguish from lung cancer

Abstract

Pulmonary alveolar proteinosis (PAP) is a disease in which surfactant accumulates in the alveoli. On computed tomography (CT), it presents as a crazy-paving pattern of bilateral diffusely thickened interlobular septa and intralobular structures from the hilar to peripheral regions. Here, we report a rare case of localized middle lobe PAP. A 59-year-old man visited our department for the diagnosis and treatment of a middle lobe ground glass nodule (GGN) that had increased in size compared with the CT findings 5 years ago. CT showed a 13-mm part solid GGN in the subpleural area and a 10-mm GGN near the hilum of the middle lobe. The patient underwent thoracoscopic right middle lobectomy because multiple lung cancer was suspected. The histopathologic examination revealed PAP. The present case of localized GGN growing in a subpleural area and in the middle lobe was considered to be a rare type of PAP.