Subtypes of peripheral adenocarcinoma of the lung: differentiation by thin-section CT.

The purpose of this study was to scrutinize morphological characteristics of thin-section CT of the histopathological subtypes of adenocarcinoma of the lung. The subjects consisted of 83 patients with 87 adenocarcinomas measuring 3 cm or less in the largest. The tumors were divided into three groups (group I: Noguchi's histological subtypes type A and B tumors, group II: type C tumors, and group III: type D, E, and F tumors). In each group, tumor size, shape (round versus polygonal), presence of air bronchogram, bubble-like areas, coarse spiculation, pleural tag, and ratio of ground glass attenuation (GGA) were evaluated. Most of the group II lesions showed polygonal shape, whereas tumors in other groups were round in shape (P<0.01). Air bronchogram and bubble-like areas of low attenuation was seen more frequently in group II compared with those in group III (P<0.01). GGA areas were largest in group I and smallest in group III (P<0.01). We believe thin-section CT findings reflect the histopathological subtypes of adenocarcinoma of the lung. The presence of air bronchogram and bubble-like areas of low attenuation areas in particular is useful to differentiate replacement growth tumors from non-replacement growth tumors.