Imaging and clinical features of sub-centimeter solitary pulmonary nodules with ground glass opacity on CT / 中华全科医师杂志

ABSTRACT

Objective:To analyze the clinical and CT imaging characteristics of sub-centimeter solitary pulmonary nodules (SSPNs) with ground glass opacity.Methods:The clinical and imaging data of 258 patients with SSPN who underwent surgical treatment in Beijing Tongren Hospital from May 2015 to May 2020 were retrospectively reviewed. There were 113 males and 145 females with a median age of 45 (range 30-84) years. The CT images of the lesions showed ground glass opacity, including 60 cases of pure ground glass nodule (pGGO) and 198 cases of mixed ground glass nodule (mGGO). The largest diameter of the lesion was ≤ 10 mm, and the lesions were all resected by video-assisted thoracic surgery, and diagnosed by postoperative pathological examination. The relationship between the lesion size and the detection rate of malignancy; the diagnostic value of CT imaging features for differentiating benign and malignant SSPN, and postoperative immunohistochemical indexes and target gene mutations for differentiating primary from metastatic lung cancer were analyzed.Results:Of the 258 patients, 59 had lesions<7 mm in diameter and 199 between 7 and 10 mm in size. There were no intraoperative deaths. The postoperative pathological examination confirmed primary bronchial lung cancer in 190 cases, metastatic lung cancer in 12 cases, and benign lung lesions in 56 cases. The detection rates of malignant lesions in mGGO and pGGO were 81.31% (161/198) and 68.33% (41/60), respectively (χ 2=4.66, P = 0.032). The detection rates of malignant lesions and primary cancer in mGGOS with diameter 7-10 mm was higher than those with diameter<7 mm[(87.01%(134/154) vs. 61.37%(27/44) and 83.77%(129/154) vs. 56.82%(24/44), χ 2=14.82, χ 2=12.93, all P<0.001 ]. The border irregularity on CT imaging was presented in 47.03% (95/202) of malignant lesions, which presented in 48.42% (92/190) of primary lung cancers; while only presented in 17.86% (10/56) of benign lung lesions (χ 2=15.46, χ 2=16.64, all P<0.001). The frequency of vascular signs was 56.44% (114/202) in lung malignant lesions, 54.74% (110/190) in primary bronchial lung cancer; while only 5.35% (3/56) in lung benign lesions (χ 2=46.16, χ 2=48.07, all P<0.001). Among mGGO patients with lesion diameter<7 mm, those with irregular lesion borders and vascular signs on CT imaging 91.30% (21/23) were pulmonary malignant lesions, while those without these two signs only 28.57% (6/21). Immunohistochemistry results showed that the primary bronchial lung cancer group had a higher positive rate of new aspartic proteinase A (Napsin A, 79.47%) and thyroid transcription factor-1 (TTF-1, 75.79%) than the metastatic lung cancer group. There were three patients with BRAF-v600e mutation in our series, and all of them were finally confirmed as metastatic thyroid cancer. Conclusion:In sub-centimeter solitary pulmonary nodules with ground glass opacity, mGGO lesions are more likely to be malignant lesions than pGGO lesions, and the lesions with larger size are more likely to be malignant. Imaging features such as irregular lesion borders and vascular signs are important in differentiating between benign and malignant lesions. For metastatic lesions, immunohistochemical and genetic testing are helpful in determining the primary tumor site.