CT diagnosis of pleural and stromal invasion in malignant subpleural pure ground-glass nodules: an exploratory study.
To assess the risk of visceral pleural invasion (VPI) and improve the diagnosis of invasive adenocarcinoma (IA) in pure ground-glass nodules (pGGNs) in contact with pleura, through a comprehensive analysis of the thin-section CT features of subpleural malignant pGGNs. CT findings and clinical information of 115 consecutive patients in our hospital between January 2012 and December 2015 who met the following criteria were retrospectively studied: (a) thin-section CT within 1 month before surgery proved pGGN in contact with pleura, and (b) the pGGN was confirmed as malignancy by surgery. Univariate analysis and a multivariate logistic regression analysis were conducted to identify the independent risk factors of IA and VPI. No pleural invasion was observed microscopically in any of the pGGNs. Univariate analysis indicated that tumour shape (p = 0.004), relative density (p = 0.038) and the existence of pleural retraction (p < 0.001) were significantly different between the invasive group and pre- or minimally invasive group. Multivariate logistic regression analysis revealed that pleural retraction (OR, 5.663; p < 0.001), lobulated tumour shape (OR, 4.812; p = 0.016) and tumour relative density greater than 1.60 (OR, 4.449; p = 0.001) were independent risk factors of IA. Pulmonary adenocarcinoma manifesting as pGGN generally does not invade the pleura. A comprehensive consideration of tumour shape, relative density and tumour-pleural relationship can independently predict IA. • This study showed that pGGN-like adenocarcinoma generally does not invade the pleura. • This study suggested that persistent pGGN with pleural retraction, lobulated shape and high relative density (> 1.60) may very likely be invasive adenocarcinoma. • Using "relative density" can reduce confounding of contrast agent and respiratory status in analysis of CT images.