Bronchioloalveolar carcinoma masked by gravity-dependent gradient on computed tomography.

A 78-year-old woman was found to have a small bronchioloalveolar carcinoma with ground-glass attenuation in the gravity-dependent gradient in the left lower lobe during a preoperative chest computed tomography (CT) evaluation, which was performed for previously-diagnosed adenocarcinoma of the right upper lobe. To remove the gravitational effect of the CT, the patient underwent a thin section CT in the prone position. Then, a ground-glass attenuation was revealed clearly in the left lower lobe. Postoperative pathological diagnosis was synchronous multiple bronchioloalveolar carcinomas, stage IA. This case suggests that focal areas of ground-glass attenuations on a thin-section CT in patients with BAC would be considered to be multicentric development of BAC. CT with the patient in the prone position helps to exclude the gravitational effect and narrow the differential diagnosis of ground-glass opacity, including localized forms of BAC.