[Pulmonary alveolar proteinosis detected by a nodular lesion on chest computed tomography].

A 74-year-old woman was admitted to our hospital for further examination of chest X-ray abnormality. The chest computed tomography (CT) revealed a nodular lesion (1.0 cm in diameter) in right lung. Bronchoscopic biopsy showed no malignant cells and bronchoalveolar lavage fluid was not milky white. We performed video-assisted thoracic surgery and a tumor was resected. Histologically, dilated alveolar areas was filled with eosinophilic materials. This finding was compatible with pulmonary alveolar proteinosis (PAP). The characteristic CT finding of PAP is ground glass opacities in both lungs with thickened alveolar septa (so-called crazy-paving appearance). The CT findings of this case (unilateral, single nodular lesion) are very rare, so we report this case with references to the literatures.