Proportion of ground-glass opacity on high-resolution computed tomography in clinical T1 N0 M0 adenocarcinoma of the lung: A predictor of lymph node metastasis

Objective: In patients with clinical T1 N0 M0 lung adenocarcinoma, we investigated whether the proportion of ground-glass opacity area measured on high-resolution computed tomography was valuable for predicting the existence of lymph node metastasis, lymphatic invasion, or vascular invasion. Methods: Between 1994 and 1999, 111 patients with clinical stage IA adenocarcinoma underwent surgical resection of the lung at our hospital. Of these, 96 patients received high-resolution computed tomography of the chest, and they constituted the study population. The tumors were semiquantitatively classified into 5 groups on the basis of the proportion of ground-glass opacity area to whole tumor shadow on high-resolution computed tomography: group I, 0%; group II, 1% to 25%; group III, 26% to 50%; group IV, 51% to 75%; and group V, 76% to 100%. Correlations of computed tomographic findings, pathologic results of lymph node metastasis and lymphatic and vascular invasion, and the histologic subtype according to the new World Health Organization classification were examined. We also investigated the characteristics of the patients with ground-glass opacity areas on high-resolution computed tomography and their value for predicting lymph node metastasis. Results: Among the 96 patients, 15 (15.6%) had mediastinal lymph node metastases, and 3 (3.1%) had hilar node metastases. Regarding the proportion of the ground-glass opacity area of the tumors, 15 (15.6%) tumors were classified as group V, 11 (11.5%) as group IV, 9 (9.3%) as group III, 22 (22.9%) as group II, and 39 (40.6%) as group I, respectively. Of the 18 patients with lymph node metastases, no patients were found in groups IV and V, 2 (22.2%) were found in group III, 4 (18.2%) were found in group II, and 12 (30.8%) were found in group I (trend P = .003), respectively. Twenty-six patients classified into groups IV and V also showed neither lymphatic invasion nor recurrence. All the smaller tumors (≤2.0 cm) in group IV or V were histologically proved to be bronchioloalveolar carcinoma. Adjusted for smoking status and other characteristics, patients without ground-glass opacity on high-resolution computed tomography had a significantly increased risk of concurrent lymph node metastasis compared with those with ground-glass opacity. Conclusion: In patients with clinical T1 N0 M0 adenocarcinoma, the proportion of ground-glass opacity area on thin-section computed tomography scans was a strong predictor for tumor aggressiveness and thus could be a useful index for planning limited surgical resection for these patients.