Clinical Characteristics
Figure 1 shows the patient inclusion flowchart. A total of 161 patients (mean age, 59.67 years ± 10.44; age range, 27–84 years), with peripheral pulmonary adenocarcinoma were included (Table 1). Sixty-two (38.50%) of the 161 patients were mean (mean age, 60. 73 years ± 10.00; age range, 33–84 years), and 99 (61.50%) were women (mean age, 59.01 years ± 10.71; age range, 27–84 years). Seventy-five patients (46.58%) of the 161 patients were diagnosed with VPI and eighty-six patients (53.42%) were diagnosed without VPI. The largest diameter of the 161 patients’ tumor was 2.32 cm ± 1.33, and the diameter ranged from 0.5-11cm.
Table 1
Clinical Characteristics of Patients with peripheral pulmonary adenocarcinoma
Characteristic
|
No. of Patients
|
Datum
|
Age of all 161 patients (y)
|
161
|
59.67 ± 10.44(27–84)
|
Male
|
|
60.73 ± 10.00(33–84)
|
Female
|
|
59.01 ± 10.71(27–84)
|
Sex of all 161 patients
|
|
|
Male
|
62
|
38.50%
|
Female
|
99
|
61.50%
|
VPI
|
|
|
Yes
|
75
|
46.58%
|
No
|
86
|
53.42%
|
Largest diameter of 161
patients’ tumor
|
161
|
2.32 ± 1.33(0.5–11)
|
Pathological type of 161 patients
|
|
|
MIA
|
3
|
1.86%
|
INMA
|
153
|
95.03%
|
IMA
|
5
|
3.11%
|
Histological subtype of 161
|
|
|
Patients
|
|
|
LPA
|
29
|
18.01%
|
APA
|
78
|
48.45%
|
MPA or SPA
|
14
|
8.70%
|
PPA
|
16
|
9.94%
|
Not available
|
24
|
14.90%
|
pT stage
|
|
|
T1
|
76
|
47.21%
|
T2
|
81
|
50.31%
|
T3 ~ T4
|
4
|
2.48%
|
Note. — Data are means ± standard deviations or percentages. Data in parentheses are ranges. pT stage= pathologic T stage, IMA= invasive mucinous adenocarcinoma, MIA = minimally invasive adenocarcinoma, INMA= invasive non-mucinous adenocarcinoma, LPA = lepidic predominant adenocarcinoma, APA = acinar predominant adenocarcinoma, MPA = micropapillary predominant adenocarcinoma, PPA = papillary predominant adenocarcinoma, SPA = solid predominant adenocarcinoma, Not available=the histological subtype was not clearly defined
|
Three patients (1.86%) of the 161 patients were diagnosed with minimally invasive adenocarcinoma (MIA) in the pathology system, one hundred and fifty-three patients (95.03%) were diagnosed with invasive non-mucinous adenocarcinoma (INMA) and five patients (3.11%) were diagnosed with invasive mucinous adenocarcinoma (IMA). Twenty-nine patients (18.01%) of the 161 patients were diagnosed with lepidic predominant adenocarcinoma (LPA) in the histology system, seventy-eight patients (48.45%) were diagnosed with acinar predominant adenocarcinoma (APA), sixteen patients (9.94%) were diagnosed with papillary predominant adenocarcinoma (PPA), fourteen patients (8.70%) were diagnosed with micropapillary predominant adenocarcinoma (MPA) or solid predominant adenocarcinoma (SPA) and for twenty-four patients (14.90%) data were not available.
Seventy-six patients (47.21%) were diagnosed with pT1 in the pT stage system, eighty-one patients (50.31%) were diagnosed with pT2, and four patients (2.48%) were diagnosed with pT3 or pT4.
Ct Characteristics
Figure 2 shows the CT imaging features of the peripheral pulmonary adenocarcinoma determined in consensus. The CT features were classified into two forms (non-interlobular PTs and interlobular PTs). Non-interlobular PTs were classified into four types (type 1, one or more linear non-interlobular PT; type 2, one or more linear non-interlobular PT with soft tissue component at the pleural end; type 3, one soft tissue cord-like non-interlobular PT; type 4, directly abutting the non-interlobular pleura). Interlobular PTs were classified into three types (type 1, pulling the interlobular pleura to the homolateral side; type 2, one or more linear interlobular PT; and type 3, pushing the interlobular pleura to the contralateral side).
In the non-interlobular PTs, nineteen patients (11.80%; eight patients [42.11%] with pleural invasion proved by pathologic analysis ) of the 161 patients had type 1 of PTs; thirty-two patients (19.88%; fifteen patients [46.88%] with pleural invasion ) had type 2 of PTs; thirty-nine patients (24.22%; twenty-two patients [56.41%] with pleural invasion ) had type 3 of PTs and forty-five patients (27.95%; nineteen patients [42.22%] with pleural invasion) had type 4 of PTs. In the interlobular PTs, nineteen patients (11.80%; eight patients [42.11%] with pleural invasion proved by pathologic analysis) of the 161 patients had type 1 of PTs; five patients (3.11%; one patient [20.00%] with pleural invasion) had type 2 of PTs and two patients (1.24%) with pleural invasion had type 3 of PTs (Table 2).
Table 2
CT Characteristics in Patients with Peripheral Pulmonary Adenocarcinoma
CT Characteristics*
Non-interlobular PTs
|
VPI n (%)
|
non-VPI n (%)
|
datum
|
Type1
Type2
Type3
Type4
|
8(42.11%)
15(46.88%)
22(56.41%)
19(42.22%)
|
11(57.89%)
17(53.12%)
17(43.59%)
26(57.78%)
|
11.80%
19.88%
24.22%
27.95%
|
Interlobular PTs
Type1
Type2
Type3
|
8 (42.11%)
1 (20.00%)
2 (100.00%)
|
11(57.89%)
4(80.00%)
0(0.00%)
|
11.80%
3.11%
1.24%
|
Note. — Data are the number of patients or percentages. Data in parentheses are percentages. PTs = pleural tags, * Based on evaluation of the last chest CT study performed before histopathologic diagnosis. |
Pathology
There were 161 patients with a definitive histopathologic diagnosis. Pathologic findings confirmed that 75 (46.58%) of the 161 patients were diagnosed with VPI, and 86 patients (53.42%) were diagnosed without VPI.
After surgery, we correlated the imaging findings with the pathologic findings. According to the characteristics of the CT images, under the ×20 magnification of hematoxylin-eosin staining, the linear pleural tags such as type 1 of non-interlobular PTs and type 2 of interlobular PTs were formed by the contraction of reactive proliferative fibrous tissue in the tumor. This was done by pulling the pleura to make it parallel, concave, and close to each other or the fibrous hyperplasia, and the thickening of the interlobular septae, along which carcinoma cells or inflammatory cells infiltrated. Type 2 of non-interlobular PTs included changes in linear PTs and terminal triangular pleural indentation. Type 3 of non-interlobular PTs were caused by the proliferative fibrous tissue in the tumor, which contracted and pulled pleura to form a V-shape shadow or caused compressive atelectasis to form a cord-like soft tissue shadow. Type 4 of non-interlobular PTs, types 1 and 3 of interlobular PTs showed tumor tissue attached to normal or thickened visceral pleura (Fig. 3).
In patients pathologically diagnosed with VPI, tumor cells were observed to penetrate the elastic fibrous boundary of the pleura and infiltrate into the pleura under the 20x microscopic scale of Elastica van Gieson staining. In patients diagnosed without VPI, the tumor cells did not break through the elastic layer of the pleura (Fig. 3).
Prognosis
Patients in this study were followed up from 2 months to 77 months after surgery. Among the 132 patients included, 50 were males and 82 were females, aged 27–84 years, with a median age of 60 years. There were 32 patients with tumor progression (19 with new malignant nodules or distant metastasis, 13 died of lung cancer). Continuous variables, including age and tumor diameter, were transformed into categorical variables. Based on our prognosis data and pathological results, the type 1 of non-interlobular PTs and type 2 of interlobular PTs were combined into a group of type 1, the type 4 of non-interlobular PTs and type 1 and 3 of interlobular PTs were combined into a group of type 4, to increase the accuracy for PFS analysis.
The results of the univariate analysis affecting tumor progression are shown in Table 3. The univariate and multivariable survival analysis curves were shown in Fig. 4. Univariate analysis showed that tumor size, histological subtype and PTs (type) were significantly associated with prognosis. Cox-proportional hazards model was further used to analyze the prognostic factors. The variables with p value < 0.15, such as sex, tumor size, VPI, PTs and histological subtype, were included in the analysis to exclude the mutual influence of each factor on the prognosis in univariate analysis. The Cox regression survival curve showed that micropapillary or solid histological subtype (HR = 5.766, 95% CI: 1.435–23.159, P = 0.014) and type 3 of non-interlobular PTs (HR = 11.058, 95% CI: 1.349–90.623, P = 0.025) were two independent risk factors for tumor progression.
Table 3: The results of univariate analysis affecting tumor progression in 132 patients
|
Variables
|
Progression(n=32)
|
Progression-free(n=100) P
|
Age(year)
≤60
>60
Sex
Male
|
14
18
18
|
0.308
56
44
0.076
32
|
Female
|
14
|
68
|
VPI
|
|
0.127
|
Yes
|
24
|
39
|
No
|
8
|
61
|
Largest diameter (cm)
≤3
>3
|
24
8
|
0.019
92
8
|
Pathological type
|
|
0.937
|
MIA
|
1
|
2
|
INMA
|
30
|
94
|
IMA
|
1
|
4
|
Histological subtype
|
|
0.036
|
LPA
|
4
|
19
|
APA
|
12
|
54
|
MPA or SPA
|
5
|
6
|
PPA
|
2
|
13
|
Not available
|
9
|
8
|
pT stage
|
|
0.222
|
T1
|
6
|
55
|
T2
|
25
|
44
|
T3~T4
Type
1
2
3
4
|
1
1
5
16
10
|
1
0.016
16
19
19
46
|
Note. — Type: different type of pleural tags
|