Value of needle confocal laser microendoscopy combined with endobronchial ultrasound bronchoscopy in the diagnosis of hilar and mediastinal lymph node lesions

Abstract

Endobronchial ultrasound bronchoscopy (EBUS) and needle confocal laser endomicroscopy (nCLE) are techniques for screening benign and malignant lesions of the hilar and mediastinal lymph node (HMLN). This study investigated the diagnostic potential of EBUS, nCLE, and combined EBUS and nCLE in HMLN lesions. We recruited 107 patients with HMLN lesions who were examined by EBUS and nCLE. A pathological examination was performed, and the diagnostic potential of EBUS, nCLE, and combined EBUS‐nCLE approach was analyzed according to the results. Among the 107 cases of HMLN lesions, 43 cases were benign and 64 cases were malignant on pathological examination, 41 cases were benign and 66 cases were malignant on EBUS examination; 42 cases were benign and 65 cases were malignant on nCLE examination; 43 cases were benign and 64 cases were malignant on combined EBUS‐nCLE examination. The combination approach had 93.8% sensitivity, 90.7% specificity, and 0.922 area under the curve, which was higher than those of EBUS (84.4%, 72.1%, and 0.782, respectively) and nCLE diagnosis (90.6%, 83.7%, and 0.872, respectively). The combination approach had a higher positive predictive value (0.908), negative predictive value (0.881), and positive likelihood ratio (10.09) than that of EBUS (0.813, 0.721, and 3.03, respectively) and nCLE (0.892, 0.857, and 5.56, respectively), whereas, the negative likelihood ratio was lower than that for EBUS (0.22) and nCLE (0.11). No serious complications occurred in patients with HMLN lesions. To summarize, the diagnostic efficacy of nCLE was better than EBUS. The EBUS‐nCLE combination is a suitable approach for diagnosing HMLN lesions.

1. INTRODUCTION

Hilar and mediastinal lymph node (HMLN), a type of mediastinal and hilar lesions, is mainly caused by lung cancer, lymphoma, sarcoidosis, tuberculosis, and other diseases. ¹ , ² In the past, radiography, computed tomography (CT), and other imaging techniques are mainly used for detecting mediastinal and hilar space‐occupying lesions, but such approaches do not provide a confirmed diagnosis. ³ Differential diagnosis of HMLN lesions can reveal whether the lymph node lesion has metastasized, provide a reliable basis for cancer staging evaluation, and help clinicians in formulating treatment plans and improving patients’ quality of life. ⁴ Mediastinoscopy and video‐assisted thoracoscopy were often used in mediastinal and hilar lesions in the past, but these two techniques are limited in terms of being relatively traumatic and conferring a high risk of injury, which restricts their clinical application. ⁵ Therefore, identifying alternative technologies has become an urgent need.

Endobronchial ultrasound bronchoscopy (EBUS) is a relatively new ultrasound‐based diagnostic technology that has been extensively used in recent years. In this technique of combining ultrasound with bronchoscopy, the ultrasonic probe is placed in front of the bronchoscope, and this device is called an integrated ultrasound fiber bronchoscope. ⁶ The EBUS can be used to directly visualize tracheobronchial mucosa, extratracheal lesions, and enlarged lymph nodes around the trachea and accurately locate the lesions. ⁷ Soon after the development of this technique, it gains attention and quickly became a new hot spot. EBUS is currently widely used in the diagnosis of mediastinal and hilar space‐occupying lesions, which can provide the diagnostic basis for unexplained mediastinal or hilar lesions. ⁸

Confocal laser endomicroscopy (CLE) is another new imaging technique based on the imaging principle of the laser scanning confocal microscope. ⁹ It enables performing high‐resolution imaging at the cellular level in vivo, which defines it as a real “optical biopsy” technology. ¹⁰ , ¹¹ In recent years, CLE has been used to detect the airways and lung tissues in real time, describe the imaging features of these structures, and differentiate the imaging characteristics in different diseases. ¹² CLE has a good prospect in auxiliary diagnosis, severity evaluation, and follow‐up examination of diseases. Needle CLE (nCLE) is a kind of CLE. ¹³ It is a flexible needle‐shaped catheter with a diameter of 0.85 mm. In this technology, the lateral resolution is 3.5 μm, the observation depth is 40–70 μm, and the field of view is 320 μm × 320 μm. ¹⁴ This technology also has a large bending angle, and it can reach the mediastinal lymph nodes through a puncture needle for exploration. ¹⁵ In 2016, Benias et al. applied nCLE in combination with fluorescein sodium for the first time to diagnose suspected malignant lymph nodes. ¹⁶ They compared nCLE images with histology findings for the preliminary identification of structures of lymph nodes and the evaluation of the imaging features of benign, malignant, and inflammatory lymph nodes, which suggests that nCLE has a certain potential in the assessment of benign and malignant lymph nodes. ¹⁶ It is advantageous to diagnose pulmonary lymph nodes with nCLE because of its small diameter, softness, and high resolution.

This study aimed to apply real‐time EBUS and nCLE technologies for the diagnosis of benign and malignant HMLN lesions and to further explore the diagnostic potential of EBUS, nCLE, and the combination of EBUS and nCLE for these lesions.

2. MATERIALS AND METHODS

2.1. Participants recruitment

Overall, 107 patients with HMLN lesions who were admitted to The Second Affiliated Hospital of Xiamen Medical College between February 2020 and December 2021 and needed a further diagnosis of their lesions by CT examination were recruited for this current study. Only one HMLN site was chosen from each patient, and site selection was made randomly, which did not affect the diagnosis and treatment of other lesions. All patients had some knowledge of the EBUS and nCLE techniques and agreed to participate in this study. The study was performed in line with the principles of the Declaration of Helsinki and received ethical approval from The Second Affiliated Hospital of Xiamen Medical College (IRB no: 2019‐157). We collected clinical information and demographic data from all patients. The disease course was collected through previous medical records, testing results, or patient self‐report information. All patients received routine treatment according to clinical diagnosis.

The inclusion criteria were as follows: (i) HMLN >10 mm in the short‐axis diameter as observed on preoperative CT examination and (ii) active cooperation to coagulation function, blood routine, and electrocardiogram (ECG) examination preoperatively. The exclusion criteria were as follows: (i) contraindications to puncture surgery; (ii) allergy to atropine, diazepam, and other anesthetic drugs; (iii) severe coagulation dysfunction and cardiopulmonary insufficiency; (iv) unable to tolerate bronchoscopy under general anesthesia; and (v) history of mental illness or drug addiction.

2.2. Preoperative preparation

All patients underwent routine blood tests (such as coagulation function) and liver and kidney function ECG before the operation, and we ensured that they had no evident abnormalities and were generally in good physical condition. Before the operation, routine fasting and drinking procedures were followed for 4 h, and during the operation, continuous oxygen inhalation, ECG monitoring, and hemodynamic index monitoring were performed. Intravenous access was established, and midazolam and pentazocine were administered intravenously for sedation and analgesia, respectively. The patients received lidocaine for local anesthesia under ECG monitoring.

2.3. EBUS and nCLE assessments

EBUS devices (BF‐UC260FOL8; Olympus Ltd, Tokyo, Japan), including an electronic scanning ultrasound mainframe and an ultrasonic optical fiber electronic bronchoscope, were used for the assessments. The patient was placed in the supine occipital position. The ultrasound bronchoscopy was inserted through one nostril or the oral cavity, and the lesion locations are studied in order of hilum, carina, and peritracheal lesions, so as to detect the lymph nodes with space‐occupying lesions and/or HMLN >10 mm. The EBUS images were recorded and saved for further evaluation.

During EBUS, the nCLE probe was introduced to a 19G Cook needle, which penetrated the target lymph node through the working channel of the ultrasound bronchoscope. At this time, the assistant gently pushed the nCLE probe forward by 5–10 mm and pressed the video development switch. An exogenous fluorescent contrast agent (2 mL of 10% sodium fluorescein) was intraoperatively infused into the patient (a skin test should be performed 30 min before infusion). Needle aspiration was performed twice or thrice for each target lesion. The number of puncture aspirations depends on obtaining clear pathological tissue strips or the patient's tolerance. Routine paraffin sectioning was done for biopsy specimens.

2.4. Final diagnosis and complications observed

As for the final diagnosis, when malignant tumor cells were observed in cytopathology or histopathological examinations, the lesion is considered to be malignant. On the contrary, when no malignant lesions were observed in the pathological examination, but a definite pathological diagnosis was made by surgery, percutaneous lung biopsy, and other biopsies, the latter was regarded as the final diagnosis. For patients who cannot collect tissues for pathological examination and are considered to have inflammatory lesions, the final diagnosis was made after clinical and imaging follow‐up, tracking the anti‐infection effect and restoration effect after treatment. Through thoracotomy or postoperative follow‐up for at least 6 months, the diagnostic efficacy of the two groups was compared, and the pathological examination and postoperative follow‐up results were used as the gold standard for diagnosis.

The results of EBUS detection were obtained from echogenic images of lymph nodes and soft tissues in the HMLN regions. The results of nCLE detection were obtained based on the following features: dark enlarged pleomorphic cells, dark cell clumps showing overlapping cell structures, and continuous movement of some cells in one direction. ¹⁵ Complications, such as pneumothorax, mediastinal infection, mediastinal emphysema, and hemorrhage, were observed.

2.5. Evaluation of the inter‐observer consistency

The inter‐observer consistency was evaluated at the end of the clinical study and after the final diagnosis of the patients. According to the nCLE standard, two endoscopic physicians, who did not participate in the clinical research, evaluated the results of nCLE and calculated the consistency between them.

2.6. Statistical analysis

SPSS 23.0 statistical software was used for data analysis in this study. The data were represented as x ± s or cases, and the t‐test and χ ² test were performed for analysis. The diagnostic potential of EBUS, nCLE, and their combination was evaluated by constructing the receiver operating characteristic (ROC) curve. p < 0.05 indicated statistical significance.

3. RESULTS

3.1. Characteristics of all patients

According to the final diagnosis, the benign group comprised 43 patients, including 26 males and 17 females, with a mean age of 50.28 ± 8.71 years, and the clinical disease course was 4.02 ± 1.22 years. The clinical course of benign HMLN is defined as the time from the first discovery of the lesion to this follow‐up visit to our hospital. In the benign group, 31 cases relapsed, and 12 were detected for the first time. The clinical course of malignant HMLN is defined as the time from the diagnosis of cancer to this follow‐up visit to our hospital. The malignant group comprised 64 patients, including 36 males and 28 females, with a mean age of 52.59 ± 9.54 years, and the clinical disease course was 4.06 ± 1.27 years. The two groups showed no significant difference between the two groups (p > 0.05, Table 1). In the benign group, 11, 8, and 24 patients had pulmonary sarcoidosis, pulmonary tuberculosis, and reactive hyperplasia of lymph nodes, respectively (Table 1). In the malignant group, 11, 33, and 21 patients had small‐cell lung carcinoma, lung adenocarcinoma, and lung squamous carcinoma, respectively (Table 1). Table 1 also presents information on the location of all HMLNs.

TABLE 1.

General clinical information of all participants.

Parameters	Benign group (N = 43)	Malignant group (N = 64)	p value
Age (years)	50.28 ± 8.71	52.59 ± 9.54	0.205
Gender (male/female)	26/17	36/28	0.665
Course of the disease (years)	4.02 ± 1.22	4.06 ± 1.27	0.874
Histopathologic diagnosis			—
Sarcoidosis (N)	11
Tuberculosis (N)	24
Reactive hyperplasia of lymph nodes (N)	8
Small cell lung carcinoma (N)		10
Lung adenocarcinoma (N)		33
Squamous cell lung cancer (N)		21
Location			—
2R (N)	0	3
2L (N)	2	4
4R (N)	11	9
4L (N)	4	8
7 (N)	14	14
10R (N)	5	9
10L (N)	0	8
11R (N)	4	4
11L (N)	3	5

3.2. Comparison of diagnostic efficacy between the two group

In Figure 1, the imaging information of a patient with an HMLN lesion was depicted. As shown in Table 2, in the benign group, 31, 36, and 39 benign patients were identified by EBUS, nCLE, and their combination respectively, while in the malignant group, 54, 58, and 60 cases were accurately identified by EBUS, nCLE, and their combination, respectively. The results of the χ ² test showed significant differences in the result of EBUS, nCLE, and their combination between the malignant and benign groups (p < 0.001, Table 2).

FIGURE 1.

(A) Contrast‐enhanced chest computed tomography image showing evident enlargement of 11L lymph nodes. (B) Endobronchial ultrasound bronchoscopy echo image showing 11L lymph node soft tissue echo image. (C) Needle confocal laser endomicroscopy image showing several dark rounds or annular cell structures in the lymph nodes, the cells are of different sizes, flowed in the same direction, and are distributed in clusters. (D) Scattered clusters of cancer cells.

TABLE 2.

Diagnosis of lymph node lesions by EBUS, nCLE and their combination.

Methods	Benign group (N = 43)	Malignant group (N = 64)	Total	p value
EBUS
Benign (N)	31	10	41	<0.001
Malignant (N)	12	54	66
nCLE
Benign (N)	36	6	42	<0.001
Malignant (N)	7	58	65
Combination
Benign (N)	39	4	43	<0.001
Malignant (N)	4	60	64

Abbreviations: EBUS, endobronchial ultrasound bronchoscopy; nCLE, needle based confocal laser endomicroscopy.

Positive and negative predictive values (PPV and NPV, respectively), and positive and negative likelihood ratios (PLR and NLR, respectively) are common measures in estimating discriminative ability and diagnostic accuracy. ¹⁷ The PPV, NPV, PLR, and NLR of the EBUS group were 0.813, 0.721, 3.03, and 0.22, respectively (Table 3). The PPV and NPV, PLR, and NLR of nCLE in the differentiation of HMLN lesions were 0.892, 0.857, 5.56, and 0.11, respectively (Table 3). The PPV, NPV, PLR, and NLR of the combined approach were 0.908, 0.881, 10.09, and 0.07, respectively, indicating that the possibility of diagnosing or excluding malignant HMLN lesions was significantly high (Table 3).

TABLE 3.

Comparison of diagnostic efficacy of different procedures.

Methods	PPV (%)	NPV (%)	PLR	NLR
EBUS	0.813	0.721	3.03	0.22
nCLE	0.892	0.857	5.56	0.11
Combination	0.908	0.881	10.09	0.07

Abbreviations: EBUS, endobronchial ultrasound bronchoscopy; nCLE, needle‐based confocal laser endomicroscopy; NLR, negative likelihood ratio; NPV, negative predictive value; PLR, positive likelihood ratio; PPV, positive predictive value.

3.3. Diagnostic potential of different methods of diagnosis

For pathological examination, which is considered the gold standard for diagnosis, the area of the curve (AUC), sensitivity, and specificity of EBUS in the diagnosis of malignant and benign HMLN lesions were 0.782 (95% confidence interval [CI] = 0.688–0.877), 84.4%, and 72.1%, respectively (Figure 2A). For the final diagnosis and a diagnosis based on cell morphology, the AUC, sensitivity, and specificity were 0.872 (95% CI = 0.795–0.948), 90.6%, and 83.7%, respectively (Figure 2B). For combined EBUS and nCLE, the AUC, sensitivity, and specificity were 0.922 (95% CI = 0.861–0.983), 93.8%, and 90.7%, respectively, which were relatively higher than those of other diagnostic methods (Figure 2C).

FIGURE 2.

Receiver operating characteristic curve of the diagnostic potential of (A) endobronchial ultrasound bronchoscopy, (B) needle confocal laser endomicroscopy, and (C) the combination of the two approaches.

3.4. Related complications and adverse reactions

No complications, such as pneumothorax, mediastinal infection, and mediastinal emphysema, occurred among the patients. After surgery, 13 patients had a relatively large amount of bleeding, but the bleeding stopped automatically without the involvement of hemostasis.

3.5. Inter‐observer consistency

A higher kappa coefficient (K) indicates higher reliable consistency. ¹⁸ The results of the kappa test revealed K = 0.808, suggesting that a high degree of consistency existed between the two endoscopic physicians in terms of diagnosis.

4. DISCUSSION

nCLE can be used for imaging the target tissue at the subcellular level, and it not only provides real‐time optical biopsy in vivo but also avoids the damage caused during sampling. ¹⁹ EBUS can also be used to obtain images of lymph nodes and surrounding tissues, which can provide a basis for differentiating pathological types according to the information displayed by ultrasound of lymph node. ²⁰ Both nCLE and EBUS have some limitations in identifying different types of HMLN, such as low sensitivity and specificity. For EBUS and nCLE, the operator should be familiar with the anatomical structure of the mediastinum and hilum, and have spatial imagination. ²¹ , ²²

EBUS is a highly useful technology for diagnosing and treating respiratory diseases, lung cancer, and other lung diseases, as well as mediastinal lymphadenopathy. It can be visualized by eye, in which we can clearly see the lesions behind the wall. In this study, 107 HMLN lesions of 107 patients were examined using EBUS and the diagnosis was made by pathological examination. The findings of the ultrasound examination showed whether the lesion is benign or malignant. The classification of lesions using EBUS shows clinical significance in distinguishing benign and malignant lymph nodes around the hilum and mediastinum. The PPV, NPV, PLR, NLR, sensitivity, specificity, and AUC of EBUS in detecting malignant lymph nodes were 0.813, 0.721, 3.03, 0.22, 84.4%, 72.1%, and 0.782, respectively. EBUS could be used as an early screening tool owing to its detection potential. Uchimura et al. use endobronchial ultrasound to detect 149 HMLN lesions of 132 patients, and the PPV and NPV for distinguishing benign and malignant lymph nodes are 78.9% and 89.0%, respectively. ²³ Images obtained from the EBUS elastography can be used to predict malignant lymph node infiltration and improve diagnostic effect. ²⁴ Consistent with previous studies, our findings indicated that EBUS is a useful diagnostic tool to differentiate HMLN lesions.

CLE can be used to perform in vivo non‐invasive histological examinations and high‐resolution real‐time dynamic imaging. ²⁵ CLE is advantageous because it provides high‐resolution and real‐time imaging and is relatively noninvasive, which makes it an important tool for application value in the research of chronic airway diseases, real‐time diagnosis of lung tumors, guided biopsy, dynamic evaluation, and follow‐up of lung diseases. ²⁶ At present, a CLE map for the digestive system has been established and used for auxiliary diagnosis. Regarding its use for diagnosis in the respiratory system, it has been in the stage of clinical research and exploration. Kramer et al. prove that observers can distinguish malignant tumor of airway or lung parenchyma from nCLE with 95% accuracy, it is proved nCLE is a feasible real‐time diagnostic tool for detecting lung cancer. ²⁷ Wijmans et al. use nCLE to explore lung malignant tumors and mediastinal lymph nodes respectively and compared the finding with those of histopathology images; they also summarize the CLE characteristics of malignant tumors. ¹⁵ The AUC, sensitivity, and specificity of nCLE in detecting HMLN lesions were 0.842, 90.6%, and 83.7%, respectively, suggesting the high accuracy of this diagnostic tool in differentiating benign and malignant HMLNs. The PPV and NPV were 0.892 and 0.857, respectively, documenting the occurrence of misdiagnosis and missed detection; however, the PLR and NLR were 5.56 and 0.11, respectively, indicating that the possibility of true‐positive and true‐negative results was high. Thus, nCLE might be used as a real‐time diagnostic tool for distinguishing HMLN. Considering the diagnostic accuracy of EBUS and nCLE, the screening ability of the combination of these two methods was revealed. The predictive accuracy of the combined EBUS‐nCLE approach was identified by constructing a ROC, which suggested that the combination approach had a high accuracy, sensitivity, and specificity. In addition to these results, the PPV, NPV, PLR, and NLR values suggested that the combined EBUS and nCLE was a highly useful combination of diagnostic technology with a high true identifying ability and a low misdiagnosis ratio. Compared with the utilization of either EBUS or nCLE, the combination approach can yield better diagnostic outcomes. Additionally, the complications and adverse reactions were documented in this manuscript. No serious complications or adverse reactions occurred in patients with extrapulmonary malignancy reported after the application of EBUS‐guided transbronchial needle aspiration and hilar lymphadenopathy. ²⁸ Chrissian et al. report that in patients with mediastinal or hilar lymphadenopathy and a low likelihood of non‐small cell lung carcinoma, no complications are observed after the appliance of EBUS‐miniforceps biopsy. ²⁹ Similarly, no patients had complications in the present study. However, the present study had a few limitations including its retrospective design and small sample size.

To sum up, the diagnostic efficacy of nCLE was better than EBUS according to the ROC curve. The combination of EBUS and nCLE had high sensitivity, specificity, and accuracy in detecting and diagnosing benign and malignant HMLN lesions. Additionally, no complications were observed in patients with HMLN lesions.

CONFLICT OF INTEREST STATEMENT

All authors declare no conflict of interest.

Zuo C‐Y, Xue K‐Y, Wu X‐M, Lin L‐C, Luo B‐Q, Chen Z‐D, et al. Value of needle confocal laser microendoscopy combined with endobronchial ultrasound bronchoscopy in the diagnosis of hilar and mediastinal lymph node lesions. Kaohsiung J Med Sci. 2023;39(9):936–942. 10.1002/kjm2.12714