Abstract: Objective  To analyze CT imaging features of lung pure ground-glass nodule (pGGN) of 1 cm or less, and to discuss the differential diagnosis value of multi-slice spiral CT (MSCT) of lung pGGN of 1 cm or less in lung infiltrating adenocarcinoma and before infiltration. Methods  A total of 103 patients with lung pGGN≤1 cm admitted to the First Hospital of Handan from January 2012 to August 2016 were selected. Of the 103 lung pGGN lesions, there were 67 preinvasive lesions (the preinvasive lesion group) confirmed by operation, including 28 atypical adenomatous hyperplasia and 39 adenocarcinoma in situ. There were 36 invasive lesions (the infiltration group), including 21 minimally invasive adenocarcinoma and 15 invasive adenocarcinoma. All the patients underwent MSCT scanning, and the lesion location, size, CT value, internal density, edge, peripheral vessel and lungtumor interface were compared between the two pathological types. The receiver operating characteristic curves of the size of the infiltrating lesion and before infiltration were drawn, and the boundary values of the size of the two kinds of pGGN were analyzed and identified. Results  The differences of the lesion location (χ²＝0.529,P=0.746), vacuole sign (χ²＝1.581, P=0.209), aerated bronchus sign (χ²=1.639, P=0.201), edge of the lesion (χ²=0.614, P=0.722) between the two groups were not statistically significant. The proportion of clear lungtumor interface in infiltration group was higher than that in preinvasive lesion group (86.11% vs. 44.78%; χ²=16.568,P＜0.001). The proportion of type Ⅰ in the classification of pulmonary vascular relationships in infiltration group was lower than that in preinvasive lesion group (5.56% vs. 41.79%; χ²=14.894,P＜0.001), and the proportion of type Ⅲ in infiltration group was higher than that in preinvasive lesion group (38.89% vs.1.49%; χ²=26.320, P＜0.001). The average maximum diameter of the infiltration group ［(0.85±0.17)cm］ was greater than that of the preinvasive lesion group ［(0.76±0.16)cm］, and the difference was statiscally significant (t=2.663, P=0.009). The boundary value to identify the size of the preinvasive and invasive lesions was 0.81 cm, and its sensitivity and specificity rates were 62.1% and 63.5%, and the area under the curve was 0.622. Conclusion  Of lung pGGN≤1 cm, invasive lesions are larger, lungtumor interface is more clear, and the proportion of type Ⅲ in the classification of pulmonary vascular relationships is bigger. MSCT can present the above imaging characteristics of lesions, and it has the important value in differential diagnosis of lung pGGN≤1 cm in infiltrating adenocarcinoma and before infiltration.

Key words: Lung neoplasms, Coin lesion, pulmonary, Tomography, spiral computed, Carcinoma in situ, Infiltration