[A case of pneumoconiosis (welder's lung) suspected to be lung cancer].

A 60-year-old man, employed as a welder for 25 years, was admitted with an abnormal shadow on chest X-ray. An ill-defined and solitary mass shadow 3 cm in diameter was subsequently detected in the left upper lung field. The mass shadow exhibited high attenuation on chest CT scan. Transbronchial lung biopsy (TBLB) revealed an organized lesion possessing a large quantity of iron. Although pneumoconiosis was suspected, the possibility of lung cancer could not be dismissed. Pneumoconiosis (welder's lung) was diagnosed after thoracotomy and examination of the resected mass. Pneumoconiosis (welder's lung) rarely presents as a solitary mass lesion.