Invasive Pulmonary Adenocarcinomas versus Preinvasive Lesions Appearing as Ground-Glass Nodules: Differentiation by Using CT Features

Purpose: To retrospectively investigate the differentiating computed tomographic (CT) features between invasive pulmonary adenocarcinoma (IPA) and preinvasive lesions appearing as ground-glass nodules (GGNs) in 253 patients. Materials and Methods: This study was approved by the institutional review board. From January 2005 to October 2011, 272 GGNs were pathologically confirmed (179 IPAs and 93 preinvasive lesions) in 253 patients and were included in this study. There were 64 pure GGNs and 208 part-solid GGNs. Preinvasive lesions consisted of 21 atypical adenomatous hyperplasias and 72 adenocarcinomas in situ. To identify the differentiating CT features between IPAs and preinvasive lesions and to evaluate their differentiating accuracy, logistic regression analysis and receiver operating characteristic (ROC) curve analysis were performed, respectively. Results: In pure GGNs, preinvasive lesions were significantly smaller and more frequently nonlobulated than IPAs (P < .05). Multivariate analysis revealed that lesion size was the single significant differentiator of preinvasive lesions from IPAs (P = .029). The optimal cut-off size for preinvasive lesions was less than 10 mm (sensitivity, 53.33%; specificity, 100%). In part-solid GGNs, there were significant differences in lesion size, solid portion size, solid proportion, margin, border, and pleural retraction between IPAs and preinvasive lesions (P < .05). Multivariate analysis revealed that smaller lesion size, smaller solid proportion, nonlobulated border, and nonspiculated margin were significant differentiators of preinvasive lesions (P < .05), with excellent differentiating accuracy (area under ROC curve, 0.905). Conclusion: In pure GGNs, a lesion size of less than 10 mm can be a very specific discriminator of preinvasive lesions from IPAs. In part-solid GGNs, preinvasive lesions can be accurately distinguished from IPAs by the smaller lesion size, smaller solid proportion, nonlobulated border, and nonspiculated margin. (C) RSNA, 2013