Pathologic and biological assessment of lung tumors showing ground-glass opacity

We evaluated the pathologic and biological aspects of lung tumors 3.0 cm or less in diameter with the appearance of ground-glass opacity (GGO).

Of 988 patients with non-small cell lung cancer who underwent operations at our institute between January 1994 and December 2004, 87 resected lung tumor specimens that showed GGO appearance on helical computed tomography were obtained from 81 patients. Forty-four lesions were pure GGO with no solid component in the tumor and 43 lesions were mixed GGO consisting of areas of attenuation with a solid component. Together with histological features, MIB1 and nm23 expression within tumors were examined immunohistochemically.

The mean tumor size in the pure GGO group was significantly smaller than that in the mixed GGO group. The composition of pathologic subtypes and biological characteristics were clearly different between the two groups. Although atypical adenomatous hyperplasia and localized bronchioloalveolar cell carcinoma of Noguchi's A and B were the predominant pathologic subtypes and nm23 negativity was rare in the pure GGO group, a high score for expression of MIB1 was often found in pure GGO tumors even though the tumors were less than 10 mm in diameter.

If the tumor is 2 cm or less in diameter, the ability of invasion and metastasis seems to be low in pure GGO tumors. However, the proliferation ability of these tumors suggests the necessity of a careful follow-up schedule if the tumor is greater than 5 mm in diameter. For mixed GGO tumors, surgical resection instead of observation is justified.