[Nodular bronchioloalveolar carcinoma with multiple small air spaces caused by bronchiolectasis]

A 67-year-old man was admitted to our hospital with a faint abnormal shadow in the right S2 on January 1995. Chest CT showed a faint abnormal shadow about 3 cm in diameter with multiple small air spaces. He was admitted again 18 months later for surgical treatment because the shadow on chest X-ray had grown. Right upper lobectomy was performed in June 1996 and pathohistological examination revealed bronchioloalveolar carcinoma. Tumor cells along the walls of the alveolus were recognized only in the periphery of the lesion. The center of the lesion was fibrotic and multiple small air spaces ranging from 0.5 mm to 10 mm in diameter were present. One cause of these air spaces was considered to be the "check valve" mechanism, but the majority of the air spaces were derived from ectatic bronchioli. These results suggested that bronchiolectasis had developed with central fibrosis only in the tumor. Central fibrosis in this case had played a significant role in determining the radiographic appearance of the lesion.