Background Less invasive adenocarcinomas (LIAs) of the lung, including adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA), are indications of sublobar resection and has a 5-year disease-free survival rate of almost 100% after surgery. By distinguishing invasive adenocarcinoma from LIA with computed tomography (CT) characteristics, it is possible to determine the extent of resection and prognosis for patients with ground-glass nodules (GGNs) before surgery. Methods We reviewed CT and pathological findings of 728 GGNs in 645 consecutive patients who received curative lung resection in a single center. Only AIS, MIA, and invasive adenocarcinoma were included. Characteristics of CT, including maximum diameter of the lesion (L_max) and maximum diameter of the consolidation (C_max), were assessed thoroughly. Results Multivariate logistic regression showed that larger L_max (p < 0.001) and nonsmooth margin (p = 0.001) were independent factors for invasive adenocarcinoma in pure GGNs (pGGNs). The optimal cut-off value of L_max was 12.0 mm. In mixed GGNs (mGGNs), multivariate analysis revealed that larger L_max (p < 0.001), larger C_max (p = 0.032), and vacuole sign (p = 0.007) were predictive factors for invasive adenocarcinoma, and the area under curve of regression model was 0.866. The optimal cut-off values of L_max and C_max were 15.4 and 5.8 mm, respectively. No node metastasis was found in 295 patients who had at least three stations of mediastinal lymph nodes dissected. Conclusion In pGGNs, larger L_max (>12.0 mm) and nonsmooth margin were reliable predictors for invasive adenocarcinoma. In mGGNs, lesions with larger L_max (>15.4 mm), larger C_max (>5.8 mm), and vacuole sign were more likely to be invasive adenocarcinoma.

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