Patients’ clinical characteristics
Seventy-nine patients (mean age: 53 ± 11 years; range: 19–79 years) were included, comprising 32 (40.5%) men (mean age: 55 ± 10.5 years; range: 36–79 years) and 47 (59.5%) women (mean age: 51 ± 11 years; range: 19–68 years). Among 79 patients with GGNs, 53 (67.1%) were confirmed by surgical resection and pathological examination, and 26 (32.9%) by disappearance during follow-up (mean follow-up time: 4.8 months ± 4.5; range: 0.5 ~ 16 months). A total of 24 resected GGNs had follow-up results (mean follow-up time: 3.0 months ± 2.9; range: 0.3 ~ 8.5 months), 22 (91.7%) GGNs had no significant change, and 2 (8.3%) GGNs showed a slight decrease in size or density. At 3 months after first detection, most of transient GGNs (19/26, 73.1%) resolved, whereas most of resected nodules (22/24, 91.7%) remained stable.
Among 79 patients, there were 40 (50.6%), 25 (31.6%), and 14 (17.7%) patients with type I, type II, and other type GGNs, respectively. There were more women (P = .041), nonsmokers (P = .003) and nondrinkers (P = .003) in type II than in other two types. Eosinophil count was higher in patients with type I GGNs than that in patients with type II and other type lesions (P < .001), and eosinophilia was observed in 3 patients with type I GGNs. Patients’ clinical characteristics are summarized in Table 1.
Table 1
Clinical features of patients with different types of benign GGNs
Clinical features | Type I (n = 40) | Type II (n = 25) | Other type (n = 14) | P value |
Sex | | | | |
Man | 20 (50.0) | 5 (20.0) | 7 (50.0) | .041‡ |
Woman | 20 (50.0) | 20 (80.0) | 7 (50.0) |
Age (y) | 53 ± 11 | 54 ± 11 | 50 ± 10 | .838& |
Current or former smoker | 18 (45.0) | 2 (8.0) | 6 (42.9) | .003§ |
Current or former drinker | 16 (40.0) | 1 (4.0) | 3 (21.4) | .003§ |
Surgically resected | 24 (60.0) | 19 (76.0) | 10 (71.4) | - |
Resolved in follow-up | 16 (40.0) | 6 (24.0) | 4 (28.6) | - |
Follow-up time (month)* | 4.5 ± 4.4 | 2.4 ± 0.5 | 7.4 ± 5.4 | - |
Mode of detections | | | | |
Accidentally found | 4 (10.0) | 4 (16.0) | 3 (21.4) | |
Found by physical examination | 29 (72.5) | 14 (56.0) | 10 (71.4) | .413§ |
Symptomatically found | 7 (17.5) | 7 (28.0) | 1 (7.1) | |
Malignancy history | 2 (5.0) | 1 (4.0) | 1 (7.1) | - |
WBC (uL− 1) | 6872 ± 2931 | 6131 ± 2900 | 6087 ± 1733 | .296& |
Eosinophil (uL− 1) | 154 ± 223 | 94 ± 100 | 70 ± 38 | ༜.001& |
Data are presented as n (%) or Means ± standard deviation. *Data are collected from patients with resolved GGNs. ‡Calculated with the Pearson χ2 test. §Calculated with the Fisher’s exact test. &Wilcoxon rank sum test. |
CT features of different types of benign GGNs
CT features of each GGN type are summarized in Table 2. There were no significant differences in their location, diameter, shape, and margin of well-defined nodules among different types (P = .384, p = .299, P = .527, and P = .540, respectively), whereas there was a significant difference in lesion border (P = .010). Benign GGNs were mainly located in the upper lobes and had irregular shape. Type II and other type GGNs were usually well-defined but had coarse margins. For each type of benign GGNs, there were no significant differences in their CT features between resolving and resected ones, except for the diameter in type II (P = .006).
Table 2
Thin-section CT features of different types of benign GGNs
CT features | Type I (n = 40) | Type II (n = 25) | Other types (n = 14) | P value |
Lesion location | | | | |
Right upper lobe | 15 (37.5) | 13 (52.0) | 6 (42.9) | .384§ |
Right middle lobe | 2 (5.0) | 2 (8.0) | 4 (28.6) |
Right lower lobe | 7 (17.5) | 4 (16.0) | 1 (7.1) |
Left upper lobe | 11 (27.5) | 4 (16.0) | 3 (21.4) |
Left lower lobe | 5 (12.5) | 2 (8.0) | 0 (0.0) |
Mean diameter (mm) | 11.4 ± 4.8 | 9.2 ± 3.3 | 9.8 ± 2.9 | .299& |
Uniformity of GGO or GGN | | | | |
Homogeneous | 18 (45.0) | 12 (48.0) | 4 (28.6) | - |
Heterogenous | 22 (55.0) | 13 (52.0) | 10 (71.4) |
Lesion shape | | | | |
Round/oval | 15 (37.5) | 6 (24.0) | 4 (28.6) | .527§ |
Irregular | 25 (62.5) | 19 (76.0) | 10 (71.4) |
Lesion border | | | | |
Ill-defined | 28 (70.0) | 9 (36.0) | 5 (35.7) | .010‡ |
Well-defined | 12 (30.0) | 16 (64.0) | 9 (64.3) |
Margin of well-defined nodules | | | | |
Coarse | 11 (91.7) | 15 (93.8) | 7 (77.8) | .540§ |
Smooth | 1 (8.3) | 1 (6.3) | 2 (22.2) |
Note. Data are presented as n (%) or Means ± standard deviation. ‡Calculated with the Pearson χ2 test. §Calculated with the Fisher’s exact test. &Wilcoxon rank sum test. |
For type I GGNs, the peripheral GGO components were frequently ill-defined (28/40, 70.0%). Most of nodules (38/40, 95.0%) only had a single high-attenuation zone with a mean diameter of 3.5 mm (range: 1.2 ~ 7.5 mm). Among the 40 high-attenuation zones, 24 (60.0%) were centric and 16 (40.0%) were eccentric, 22 (55.0%) were regular (round or oval) and 18 (45.0%) were irregular, 38 (95.0%) had blurred edge and 2 (5.0%) had clear edge, and 32 (80.0%) connected to adjacent blood vessels (arteries: 20/32, 62.5%, veins: 12/32, 37.5%) (Fig. 3, Fig. 4).
For 25 type II GGNs, 14 (56.0%) abutted the pulmonary artery branches and 11 (44.0%) abutted the pulmonary vein branches, but these vessels had no significant changes in morphology (Fig. 5, Fig. 6). In addition, 12 (48.0%) and 13 (52.0%) cases were homogeneous and heterogeneous, respectively.
Fourteen other type GGNs included 5 (35.7%) lesions with bubble lucency, 4 (28.6%) clinging to pleura or fissure with wide base, 3 (21.4%) with faint density and ill-defined border, and 2 (14.3%) with significant irregular shape.
Pathological findings
The pathological findings of 53 surgically resected GGNs were reviewed. In 24 type I GGNs, the pathological components were thickened alveolar walls with inflammatory cells, fibrous tissue and exudation (22, 91.7%) and granuloma (2, 8.3%) for internal high-attenuation zones, and a small amount of inflammatory cell infiltration with (21, 87.5%) and without (3, 12.5%) fibrous tissue proliferation for peripheral GGOs. The main pathological findings were similar for 19 type II and 10 other type GGNs, including focal interstitial fibrosis (type II GGNs: 8/19, 42.1%; other type GGNs: 4/10, 40.0%) and fibrous tissue proliferation with inflammatory cell infiltration (type II GGNs: 11/19, 57.9%; other type GGNs: 6/10, 60.0%).