In TS-CT scan images, consolidation areas represent mostly the foci of fibrosis or tumors of a solid growth pattern, whereas GGO areas reflect areas of a growth pattern of tumor cells replacing alveolar lining cells such as BAC. Because the fibrotic foci increase with the progression of the tumor, and because these areas and advanced adenocarcinomas with a solid growth pattern demonstrate consolidation areas on CT scans, it is suggested that the percentage of the consolidation or GGO areas relative to the tumor is a prognostic indicator. Many investigators5–22 have reported on the correlation among TS-CT scan findings, pathologic findings, and prognosis. These studies have shown that GGO ratios were very much associated with BAC ratios and had favorable prognostic factors. However, the methods used to calculate the percentage of GGO areas (ie, GGO ratio) differ in different articles. Besides, we have few articles that have accurately determined the presence of noninvasive carcinoma, which was defined as a tumor without lymph node metastasis, pleural invasion, vascular invasion, and lymphatic invasion, by TS-CT scan images. The parameters used to calculate the GGO ratio that have previously been reported are as follows: a GGO/tumor area ratio,5–10; a consolidation/tumor dimension ratio11–14; a GGO/tumor volume ratio15–; an area ratio of tumor on mediastinal window to that on the lung window16–17; a product of the dimension ratio of the tumor on the mediastinal window to that on lung window18–20; and a maximum dimension of tumor on the mediastinal window.21 Matsuguma et al8 reported on the relation between the proportion of the GGO and both clinicopathologic characteristics and tumor recurrence in patients with clinical T1N0M0 adenocarcinoma. In this study, the patients with a GGO ratio of ≥ 50% seen on high-resolution CT scans had neither lymph node metastasis nor lymphatic invasion and were alive without cancer recurrence. Ohde et al12 reported the relation between the proportion of consolidation to GGO and pathologic invasive findings in patients with lung adenocarcinomas ≤ 3.0 cm. They showed that all tumors in which the ratio of the greatest diameter of consolidation to that of the tumor was ≤ 50% had neither lymph node metastasis nor vessel invasion and 5-year survival rate of 95.7%. Although only one cancer relapse was seen in tumors with a ratio of the greatest diameter of consolidation to that of the tumor of ≤ 50% in the study by Ohde et al12; the methods used to calculate the GGO ratio in these two studies8,12 may be useful in defining noninvasive cancer. On the other hand, several investigators16–20 used not only lung window images but also mediastinal window images to classify the tumors on TS-CT scan images. Kondo et al16 used a ratio of the tumor area on the mediastinal window images to that on lung window images in patients with pulmonary adenocarcinoma of ≤ 2.0 cm, and showed that the tumors with a ratio of ≤ 50% had no lymph node metastasis, rare vascular invasion, and no cancer relapse. Okada et al18 and Shimizu et al20 used the tumor shadow disappearance rate, which was determined from the product of the maximum dimension of the tumor and the largest dimension perpendicular to the maximum axis on both pulmonary and mediastinal window images on TS-CT scan, as previously described by Takamochi et al.22 They showed that the tumors with a tumor shadow disappearance rate of ≥ 50% had no lymph node metastasis, rare vascular invasion, and no cancer relapse in patients with lung adenocarcinomas ≤ 2.0 cm in diameter. However, the methods used to classify the tumors in these studies with both pulmonary and mediastinal window images could not completely discriminate the tumor without invasive findings (ie, vascular, lymphatic, and pleural involvement) from the other. In contrast, the present study showed that the air-containing-type tumor did not have lymph node metastasis, pleural involvement, vessel invasion, or lymphatic permeation, and did not recur after resection. These results suggest that the air-containing-type tumor should be defined as a noninvasive cancer.