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The use of computed tomography (CT) scans has increased the opportunities to detect small nodular shadows in peripheral lung fields. Intrapulmonary lymph nodes (IPLNs) are sometimes identified among these nodular shadows, and a differential diagnosis is often difficult. However, few descriptions of the CT findings of IPLNs, with regard to their potential for the differential diagnosis of lung cancer, have been published.
From 2006 through 2011, 606 patients underwent thoracic surgery for pulmonary nodules. Nine patients (1.5%) had pathologically diagnosed IPLNs. We retrospectively reviewed the clinicopathological features and thin-section CT findings of the patients with IPLNs. We also compared these IPLN patients with 17 patients having small-sized lung cancer.
In six cases, the nodules were round, and linear density extending from the IPLNs was visualized in seven nodules. The nodules in IPLNs were located in the lower lobe, and the nodule borders were clearer than those of lung cancers. Six out of nine nodules were round, and linear densities were more easily visualized for the IPLNs.
Medical specialists need to be familiar with the discriminative features of thin-slice CT for IPLNs not only to avoid performing unnecessary operations, but also to prevent the mis-staging of lung cancer.
computed tomography examination;intrapulmonary lymph node;lung cancer;small nodular shadow;surgical resection
The widespread use of computed tomography (CT) scanning has increased the opportunities to detect small nodular shadows in peripheral lung fields,1 which are difficult to diagnose pathologically. Thus, most of these cases are resected in order to diagnose and treat them. Intrapulmonary lymph nodes (IPLNs) are sometimes resected based on a diagnosis of a lung cancer or lung metastasis.2 Therefore, a more accurate diagnosis of IPLNs is essential not only to avoid unnecessary surgery, but also to prevent the mis-staging of lung cancer.
We reviewed the clinicopathological features and thin-section CT findings of nine IPLNs. Furthermore, the IPLNs were compared with small-sized lung cancers to define their discriminative features.
The institutional Review Board approved this study. From 2006 through 2011, 606 patients underwent thoracic surgery for pulmonary nodules in the Second Department of Surgery at the University of Occupational and Environmental Health, Kitakyushu, Japan. A total of 458 patients were diagnosed with lung cancer, 73 with metastatic lung tumors, 52 with inflammatory pulmonary nodules, and 14 with other forms of lung cancer. Nine patients (1.5%) were pathologically diagnosed with IPLNs. The pathological findings revealed that all these patients showed anthracosis, and two of three IPLN cases with progression show lymphoid follicles. We retrospectively reviewed the age, sex, smoking history, inhalation of dust, progression of nodules, number of nodules, nodule size, site, location, border, shape, distance from the pleura, and linear density. In the same period, 17 patients had small (<10 mm) solid tumors detected in thin-section CT. We compared the nine IPLN patients with the 17 lung cancer patients with regard to their clinicopathological features and thin-section CT findings.
The evaluations at admission included a physical examination, chest roentgenography, an analysis of blood chemistry, and measurements of tumor markers. Chest and abdominal CT, brain magnetic resonance imaging, and a bone scintiscan or positron emission tomography/CT examination were performed prior to surgery. A definite diagnosis was not obtained by bronchoscopic examination in all IPLNs patients. Therefore, video-assisted thoracic surgery was performed after obtaining informed consent from the patients to obtain a larger tissue specimen, because the presence of a malignant tumor could not be ruled out.
Whole-lung CT scans were obtained with a 16- or 64-detector row CT scanner (Aquilion 16 or 64, Toshiba Medical Systems, Tokyo, Japan) using the following parameters: 2.0 mm section width with 2.0 mm reconstruction interval, pitch (ratio of table travel per rotation to total beam width) of 15,120 kVp, and 300 mA. Each CT image was displayed and evaluated using a standard lung window (window width, 1600 HU; window level, –600 HU) and a mediastinal window (window width, 350 HU; window level, 50 HU) on a high-resolution monitor.
The two groups were compared using the Chi-square test, and logistic regression models were constructed using a logistic regression analysis. The odds ratios and 95% confidence intervals were calculated for each variable. The differences were considered to be significant for p < 0.05. The data were analyzed using the Stat View software package (Abacus Concepts, Inc., Berkeley, CA, USA).
We encountered nine cases of IPLNs, discovered by chest radiography or chest CT (Fig. 1). The clinical data of the patients with IPLNs are summarized in Table 1. All the patients were Japanese. They included nine males and two females, and their ages ranged from 38 to 73 years, with a mean of 60.0 years. All the male IPLN patients were heavy smokers (Brinkman index >400). Three patients had a past history of malignancy and had inhaled dust at their place of work. The thin-section CT findings of IPLNs are summarized in Table 2. In all cases of IPLNs, nodules were located in the lower lobe. They did not have calcification. Their sizes ranged from 4 to 8 mm (mean, 6.2 mm). In five and four cases, nodules were located in the right and left lobes, respectively. Three cases had progression of their nodule size for a mean follow-up period of 3.7 months and two cases had multiple nodules. The distance from the pleura ranged from 0 to 18 mm (mean, 3 mm). In six cases, the nodules were round, and linear density extending from the IPLNs was visualized in seven nodules. Neither enhancement in contrast nor pleural indentation was detected in the IPLNs.
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Figure 1. (A) Chest computed tomography revealed a small, round nodule in the lower lobe (case 2). (B) An angular and partly spiculated nodule shown in the lower lobe (case 5). |
Case | Age | Sex | Smoking | Known malignancy | Inhalation of dust |
---|---|---|---|---|---|
1 | 61 | F | No | — | Yes |
2 | 60 | M | Yes | — | No |
3 | 65 | M | Yes | Renal cell carcinoma | Unknown |
4 | 56 | M | Yes | — | No |
5 | 38 | M | Yes | — | No |
6 | 67 | M | Yes | Melanoma | Yes |
7 | 73 | M | Yes | — | No |
8 | 70 | M | Yes | Malignant tumor of the soft plate | Yes |
9 | 50 | F | No | — | No |
IPLN = intrapulmonary lymph node.
Case | Size (mm) | Site | Progression | Number of nodules | Distance from pleura (mm) | Shape | Spiculation | Enhancement | Pleural indentation | Linear density |
---|---|---|---|---|---|---|---|---|---|---|
1 | 4 | Left | Yes | Multiple | 11 | Round | − | − | − | Yes |
2 | 6 | Right | No | Single | 0 | Round | − | − | − | Yes |
3 | 4 | Left | No | Single | 6 | Round | − | − | − | Yes |
4 | 8 | Right | No | Single | 1 | Round | − | − | − | Yes |
5 | 6 | Right | No | Single | 10 | Angular | + | Unknown | − | Yes |
6 | 6 | Left | No | Multiple | 3 | Angular | − | − | − | Yes |
7 | 8 | Left | Yes | Single | 18 | Angular | + | − | − | Yes |
8 | 6 | Right | No | Single | 0 | Round | − | − | − | No |
9 | 8 | Right | Yes | Single | 0 | Round | − | − | − | No |
CT = computed tomography; IPLN = intrapulmonary lymph node.
The clinicopathological features and CT findings in our cases of IPLNs and lung cancer less than 10 mm in diameter are summarized in Table 3. In the patients with IPLNs, all nodules were located in the lower lobe, and the nodule borders were clearer than those of the tumors. Six out of nine nodules were round, and linear densities were more easily visualized for the IPLNs. No significant correlation with age, sex, smoking history, inhalation of dust, progression, number of nodules, nodule size, site, and distance from the pleura was identified between IPLNs and small-sized lung cancer.
Variable | Category | IPLNs (n = 9) | Lung cancer (n = 17) | p |
---|---|---|---|---|
Age | ≥60 | 6 | 16 | 0.065 |
<60 | 3 | 1 | ||
Sex | Male | 7 | 11 | 0.492 |
Female | 2 | 6 | ||
Smoking history | Yes | 7 | 13 | 0.940 |
No | 2 | 4 | ||
Inhalation of dust | Yes | 3 | 4 | 0.751 |
No | 5 | 9 | ||
Unknown | 1 | 4 | ||
Progression | Yes | 3 | 8 | 0.500 |
No | 6 | 9 | ||
Number of nodules | Single | 7 | 14 | 0.778 |
Multiple | 2 | 3 | ||
Size | ≤5 mm | 2 | 2 | 0.080 |
>5 | 7 | 15 | ||
Site | Right | 5 | 12 | 0.443 |
Left | 4 | 5 | ||
Location | Upper/middle | 0 | 14 | <0.001 |
Lower | 9 | 3 | ||
Border | Clear | 9 | 8 | 0.007 |
Unclear | 0 | 9 | ||
Shape | Round | 6 | 0 | <0.001 |
Angular | 3 | 17 | ||
Distance from pleura | ≤10 mm | 7 | 13 | 0.940 |
>10 mm | 2 | 4 | ||
Linear density | Yes | 7 | 6 | 0.039 |
No | 2 | 11 |
CT = computed tomography; IPLN = intrapulmonary lymph node.
Linear density was identified as a predictor for IPLNs in a univariate analysis (p = 0.050) ( Table 4).
Variable | OR | 95% CI | p |
---|---|---|---|
Age | 8.000 | 0.690–92.725 | 0.096 |
Sex | 1.909 | 0.297–12.264 | 0.496 |
Smoking history | 1.076 | 0.156–7.407 | 0.940 |
Inhalation of dust | 2.597 | 0.462–14.706 | 0.278 |
Progression | 1.778 | 0.331–9.555 | 0.503 |
Number of nodules | 0.750 | 0.101–5.577 | 0.779 |
Size | 2.143 | 0.248–18.502 | 0.488 |
Site | 0.521 | 0.097–2.793 | 0.446 |
Distance from pleura | 0.615 | 0.104–3.663 | 0.593 |
Linear density | 6.410 | 0.999–41.667 | 0.050 |
CI = confidence interval; IPLN = intrapulmonary lymph node; OR = odds ratio.
Because of the widespread use of CT,1 the differential diagnosis of previously undetectable small pulmonary nodular shadows has become more important. In the present study, we investigated a series of Japanese patients with IPLNs and lung cancer less than 10 mm in diameter that were difficult to diagnose prior to surgery.
Our findings demonstrate five important points regarding the clinical characteristics of IPLNs:
We searched the Japanese cases of IPLNs described for detailed clinical factors in published reports since thin-slice CT appeared in Japan in 1998.5 A total of 48 cases of IPLNs, including our nine cases (Table 5) and the 17 lung cancer patients in this study, were reviewed. Old age, location in the lower lobe, and a clear border of the opacity were identified as predictors for IPLNs in a univariate analysis (Table 6). Furthermore, multivariate logistic regression models indicated that the location in the lower lobe was an independent predictor for IPLNs (p = 0.009), while a clear border for the opacity had a borderline correlation (p = 0.062) ( Table 7).
Variables | Category | Number (%) |
---|---|---|
Age | ≥60 | 28 (58.3) |
<60 | 20 (41.7) | |
Sex | Male | 28 (58.3) |
Female | 20 (41.7) | |
Smoking history | Yes | 24 (50.0) |
No | 11 (22.9) | |
Unknown | 13 (27.1) | |
Inhalation of dust | Yes | 1 (2.1) |
No | 15 (31.3) | |
Unknown | 32 (66.6) | |
Progression | Yes | 4 (8.3) |
No | 3 (6.3) | |
Unknown | 41 (85.4) | |
Number of nodules | Single | 42 (87.5) |
Multiple | 6 (12.5) | |
Size (mm) | ≤5 | 16 (33.3) |
>5, ≤10 | 27 (56.3) | |
>10 | 5 (10.4) | |
Site | Right | 31 (64.6) |
Left | 14 (29.1) | |
Bilateral | 3 (6.3) | |
Location | Upper | 3 (6.3) |
Middle | 13 (27.1) | |
Lower | 32 (66.6) | |
Border | Clear | 23 (47.9) |
Unclear | 2 (4.2) | |
Unknown | 23 (47.9) | |
Shape | Round | 17 (35.4) |
Angular | 18 (37.5) | |
Unknown | 13 (27.1) | |
Distance from pleura (mm) | ≤10 | 29 (60.4) |
>10 | 2 (4.2) | |
Unknown | 17 (35.4) |
IPLN = intrapulmonary lymph node.
Variables | OR | 95% CI | p |
---|---|---|---|
Age: <60 y | 9.778 | 1.133–84.382 | 0.038 |
Sex: male | 1.712 | 0.499–5.882 | 0.393 |
Number of nodules: single | 2.893 | 0.432–19.385 | 0.274 |
Size: ≤5 mm | 3.947 | 0.749–20.811 | 0.106 |
Site: right | 0.926 | 0.251–3.425 | 0.908 |
Location: lower | 10.417 | 2.375–45.455 | 0.002 |
Border: clear | 15.187 | 2.710–85.116 | 0.002 |
Distance from pleura: ≤10 mm | 2.667 | 0.518–13.699 | 0.241 |
CI = confidence interval; IPLN = intrapulmonary lymph node; OR = odds ratio.
Variables | OR | 95% CI | p |
---|---|---|---|
Age: <60 y | 2.039 | 0.126–33.015 | 0.616 |
Sex: male | 3.425 | 0.358–33.333 | 0.285 |
Number of nodules: single | 6.478 | 0.334–125.807 | 0.217 |
Size: ≤5 mm | 3.476 | 0.266–45.492 | 0.342 |
Site: right | 1.502 | 0.117–19.231 | 0.755 |
Location: lower | 33.333 | 2.387–50.000 | 0.009 |
Border: clear | 23.392 | 0.849–644.244 | 0.062 |
Distance from pleura: ≤10 mm | 7.752 | 0.350–166.667 | 0.195 |
CI = confidence interval; IPLN = intrapulmonary lymph node; OR = odds ratio.
In conclusion, IPLNs should be taken into consideration in the differential diagnosis of small nodular lesions in the lung. We consider that the round lesions with clear borders located in the lower lobe and with linear densities on thin-section CT scan are the most important characteristics of IPLNs. With the dramatic upsurge in early detection of ever smaller lung nodules through the development of radiographic tools, many surgeons have become concerned about the unified treatment of these small lesions, even though thoracoscopic surgery can make such treatments less invasive and easier to perform.7
Published on 26/05/17
Submitted on 26/05/17
Licence: Other
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