Ground-glass nodules of the lung in never-smokers and smokers: clinical and genetic insights

Ground-glass nodules (GGNs) on computed tomography (CT) are hazy lesions that do not obscure underlying bronchial structures or pulmonary vessels. GGNs are manifestations of both malignant and benign lesions, such as focal interstitial fibrosis, inflammation, or hemorrhage (1). However, slowly growing or stable GGNs are early lung cancers or their preinvasive lesions, atypical adenomatous hyperplasia (AAH) or adenocarcinoma in situ (AIS). AAH, AIS, and lepidic predominant lung adenocarcinomas grow along preexisting alveolar structures (2), which maintain the air space. Therefore, these lesions appear as GGNs on CT. GGNs are classified into pure GGNs and part-solid GGNs that have both ground-glass and solid components (Figure 1A)