Objective:To evaluate the value of the crescent sign for predicting the invasiveness of lung adenocarcinoma presenting as pure ground-glass nodule (pGGN).Methods:The clinical, pathological and imaging data of 316 patients (320 pGGNs) confirmed lung adenocarcinoma by surgery and pathology from July 2013 to June 2018 in the First Affiliated Hospital of Wenzhou Medical University were retrospectively analyzed. All pGGNs were divided into preinvasive group (148 pGGNs) and invasive group (172 pGGNs) according to histopathology. Logistic regression analysis was used to determine the risk factors for invasiveness of pGGN, and the ROC curve analysis was performed on each risk factor.Results:Crescent sign was found in 24 cases (16.2%) in the preinvasive group and 49 (28.5%) in the invasive group, and the difference between the two groups was statistically significant (χ2=6.804 ,P=0.009).There were statistically significant differences in patient′s age, lesion size, shape, lobulation sign, and vascular stretch sign between the two groups ( P<0.05). The ROC curve showed that with the lesion size 10.5 mm as the optimal cut off value, the sensitivity for differential diagnosis of preinvasive and invasive lesions was 65.7%, the specificity was 61.5%, and the area under the curve was 0.666. Logistic regression analysis showed that maximum diameter of the lesion ≥10.5 mm, irregular shape, crescent sign and vascular stretch were independent risk factors of invasiveness of pGGN, and the OR value (95%CI) were 3.192 (1.981-5.144), 3.672 (1.545-8.725), 1.972 (1.104-3.521), and 2.026 (1.087-3.777), respectively. A logistic model was established based on the above four independent risk factors, and the area under curve was 0.711 (95%CI 0.655-0.768). Conclusion:Crescent sign can effectively reflect the invasiveness of pGGN. Maximum diameter of the lesion ≥10.5 mm, irregular shape, crescent sign and vascular stretch sign are independent risk factors of invasiveness of pGGN.