Endobronchial ultrasound-guided transbronchial cryobiopsy through a working channel potentially improving safety and efficacy

Abstract

Endobronchial ultrasound (EBUS)-guided transbronchial cryobiopsy (TBCB) is a novel method for the biopsy of hilar and mediastinal lesions. Conventional cryobiopsy requires simultaneous removal of the cryoprobe and EBUS scope from the airway, resulting in delayed observation of the biopsy site and application of hemostasis, which may lead to an increased risk of complications, especially bleeding. Moreover, during repeated passes of the cryoprobe, re-identification of the lesion is time-consuming. We developed a novel method for direct collection through a working channel during EBUS-TBCB. We performed the procedure under local anesthesia without intubation. After EBUS-transbronchial needle aspiration, the cryoprobe was introduced into the target lesion through the puncture tract for real-time EBUS visualization. A freezing time of up to 4 s allowed the cryobiopsy specimens to pass through the working channel. Retaining the EBUS scope within the airway allowed immediate observation of the biopsy site, and to immediately suction and apply hemostasis using an EBUS balloon, which led to safer cryobiopsy even without intubation. The next cryopass could then be performed. In our two representative cases, we made a definite diagnosis with three and four cryobiopsy specimens, with procedure lengths of 2.2 and 3.0 min, respectively. Only mild bleeding was observed in both cases.

Highlights

• •EBUS-TBCB is a novel biopsy method for hilar and mediastinal lesions.
• •The conventional method needs simultaneous removal of the cryoprobe and EBUS scope.
• •We developed a novel technique of direct collection through a working channel.
• •We perform EBUS-TBCB with a freezing time up to 4 s without removal of the scope.
• •This technique allows a safe and prompt EBUS-TBCB procedure.

1. Introduction

Recently, endobronchial ultrasound (EBUS)-guided transbronchial cryobiopsy (TBCB) was developed as an advanced technique for EBUS-transbronchial needle aspiration (TBNA) and intranodal forceps biopsy (IFB) [[1], [2], [3], [4], [5], [6], [7]]. EBUS-TBNA is the simplest technique, but the diagnostic yield for benign conditions and uncommon mediastinal malignancies, and success rate for genetic analyses are inadequate [6]. EBUS-IFB is a more aggressive and complicated technique when introducing forceps through the airway tract but may improve diagnostic yield compared to EBUS-TBNA [6,7]. EBUS-TBCB is a biopsy method similar to EBUS-IFB that allows for larger specimen collection with fewer tissue crush artifacts compared to EBUS-IFB [4]. When compared with EBUS-TBNA, EBUS-TBCB revealed a higher diagnostic yield for benign conditions (94 % vs. 67 %, p = 0.0009), uncommon malignant mediastinal malignancies (91.7 % vs. 25 %, p = 0.001), and a high success rate for genetic testing (93–97 % vs. 73.5–79 %, p = 0.001) [6].

In contrast, unlike EBUS-TBNA and IFB, conventional EBUS-TBCB requires simultaneous rapid removal of the cryoprobe along with the EBUS scope for specimen collection and subsequent bronchoscope reinsertion to assess bleeding and other complications [[1], [2], [3], [4], [5], [6]]. For repeat cryopasses, removal of the EBUS scope each time requires time-consuming re-identification of the target lesion.

Recently, in transbronchial lung cryobiopsy (TBLC) for peripheral pulmonary lesions, the effectiveness of non-intubated cryobiopsy has been reported [8]. A short freezing time with a 1.1-mm ultrathin cryoprobe allowed direct collection (DC) of the specimen through the working channel without removal of the bronchoscope. To overcome the shortcomings of conventional EBUS-TBCB, we applied the DC method and are currently conducting prospective feasibility trials. Herein, we report the outcomes of two cases of non-intubated EBUS-TBCB performed using the DC method. This study was approved by the Ethics Committee of Tokyo Metropolitan Cancer and Infectious Diseases Center, Komagome Hospital (approval number: 2025-1).

2. Case presentation

Case 1

A 68-year-old man was diagnosed with bilateral hilar and mediastinal lymphadenopathy using chest radiography and computed tomography (CT) (Fig. 1A). Elevated levels of the soluble IL-2 receptor, ACE, and lysozyme suggested sarcoidosis. Although EBUS-TBNA was conducted from the station 7 lymph node (LN), a definitive diagnosis could not be made; thus, this patient was referred to our department. Because of the lack of a diagnosis using EBUS-TBNA alone, we combined EBUS-IFB and the DC method for TBCB.

The patient received intravenous midazolam and fentanyl for sedation and analgesia, respectively. We approached the station 4R LN using a EBUS scope (UC-260FW; Olympus, Tokyo, Japan). Lidocaine 2 % was administered to the airways through a working channel. Swelling at the station 4R LN was evaluated using EBUS, and three passes of TBNA were performed using a 22-gauge needle (NA-U401SX, Olympus, Japan). This procedure also created an airway tract for EBUS-IFB and TBCB. Subsequently, EBUS-IFB was performed three times using 1.2-mm miniforceps (CoreDx, Boston Scientific, Boston, MA, USA), followed by the DC method of EBUS-TBCB (Fig. 1B). The biopsy valve was removed prior to cryobiopsy (Fig. 2). Using the same procedure as for EBUS-IFB, a 1.1-mm cryoprobe (Erbe Elektromedizin GmbH, Tübingen, Germany) was inserted into the LN via the created tract under real-time EBUS guidance (Fig. 1C). After activation for up to 3 s, the cryoprobe was quickly removed from the working channel. Samples were retrieved by thawing in saline and then fixed in formalin. As the scope remained in the trachea, suction was possible and compression was performed immediately with an EBUS balloon during sample collection. This procedure was repeated thrice. The procedure times for EBUS-IFB and TBCB using the DC method (from the insertion of the forceps or cryoprobe into the EBUS scope to their final removal from the working channel) were 3.7 and 2.2 min, respectively. Minor bleeding was observed.

On pathological examination, granulomas with clusters of histiocytes without necrosis were observed in all EBUS-TBNA, IFB, and TBCB specimens, suggesting a diagnosis of sarcoidosis (Fig. 1D and E). The cryobiopsy yielded a larger specimen than the one obtained with forceps (2.6 and 0.6 mm², respectively) with less crush artifact.

Case 2

An 81-year-old male with a history of heavy smoking complained of difficulty swallowing. He had undergone colectomy for stage III colon cancer seven months prior and was subsequently lost to follow-up. CT revealed a mediastinal tumor extending to the left hilum and compressing the esophagus and left main bronchus, with no other abnormal findings (Fig. 3A). Esophageal cancer had been suspected during his previous hospitalization, but a gastroscopy had showed only extrinsic compression of the esophagus; thus, we chose a transbronchial biopsy. Routine exploration of the airway revealed slight mucosal erythema of the left main bronchus. To differentiate between primary lung cancer and extrathoracic metastases, including from colon cancer, a sufficient sample size was needed. Furthermore, owing to the patient's age, it was essential to avoid complications; thus, we chose TBNA with the DC method of EBUS-TBCB. The examination was similar to that used for case 1. After performing three passes of TBNA from the left main bronchus using a UC-290FW (Olympus, Tokyo, Japan), the DC method of EBUS-TBCB was performed. Four specimens were harvested through a working channel with freezing times of 2–4 s (Fig. 3B). The DC examination time was 3.0 min. Minor bleeding was observed.

On pathological examination, atypical cells with increased chromatin and irregular nuclei were observed proliferating and forming glandular structures; consistent with poorly differentiated adenocarcinoma (Fig. 3C). The area of entire tissue was 6.5 mm². Based on negative CDX2 and SATB2 and positive TTF-1 testing, the patient was diagnosed with primary lung cancer. Molecular and immunological analyses were not performed by the pulmonologist but were deemed possible in the cryobiopsy specimen by the pathologist.

Fig. 1.

Case 1. (A) Computed tomography reveals bilateral hilar and mediastinal lymphadenopathy. (B) Doppler ultrasound findings during endobronchial ultrasound (EBUS)-guided intranodal forceps biopsy. The 1.2-mm miniforceps (arrowhead) are introduced into the lymph nodes. (C) Doppler ultrasonography findings on EBUS-TBCB. The 1.1-mm cryoprobe (arrowhead) is inserted into the lesion. (D) Pathological findings. Granulomas with clusters of histiocytes, but without necrosis, are observed, leading to the diagnosis of sarcoidosis. (E) The cryobiopsy specimen is larger than the forceps and has fewer crush artifacts. EBUS-TBCB, endobronchial ultrasound-guided transbronchial cryobiopsy.

Fig. 2.

Direct collection through the working channel in EBUS-TBCB. After removal of the biopsy valve, the 1.1-mm cryoprobe passes through the working channel, and enters the target lesion via an airway tract created by the EBUS needle. After cooling, the cryoprobe is immediately retrieved though the working channel. EBUS-TBCB, endobronchial ultrasound-guided transbronchial cryobiopsy.

Fig. 3.

Case 2. (A) Computed tomography shows the 4.9-cm mediastinal tumor extending to the left hilum. The compression of esophagus (arrow) and left main bronchus (arrowhead) is presented. (B) Doppler ultrasound findings of EBUS-TBCB. The 1.1-mm cryoprobe (arrowhead) is inserted into the lesion. (C) Pathological findings. Atypical cells with increased chromatin and irregular nuclei proliferating and forming a glandular structure, consistent with a poor differentiated adenocarcinoma. EBUS-TBCB, endobronchial ultrasound-guided transbronchial cryobiopsy.

3. Discussion

This report describes two representative cases in which non-intubated EBUS-TBCB was performed using the DC method. EBUS-TBCB is a novel transbronchial biopsy method for hilar and mediastinal lesions [[1], [2], [3], [4], [5], [6]]. EBUS-TBCB has contributed to improved diagnostic yields for benign conditions, uncommon mediastinal malignancies, and success rates of molecular and immunological analyses [[1], [2], [3], [4], [5], [6]]. Hence, the indications for EBUS-TBCB in each case included misdiagnosis by EBUS-TBNA alone and a benign condition in case 1, and a malignancy of unknown origin and the possible need to perform molecular and immunological analyses in case 2.

Conventional EBUS-TBCB is performed by simultaneously retrieving the EBUS scope and cryoprobe [[1], [2], [3], [4], [5], [6]], during which delayed hemostasis and time consumption from multiple cryo-passes are problematic. Therefore, we have developed a DC method for EBUS-TBCB. Our DC method with an ultrathin cryoprobe and a short freezing time eliminated the need for the removal of the EBUS scope from the airway, overcoming these problems. To the best of our knowledge, limited evidence has been published to support this method.

Our DC method is similar to that of EBUS-IFB. EBUS-IFB and TBCB require insertion of the forceps and cryoprobe through the small airway tract created by the TBNA needle or high-frequency needle-knife [[1], [2], [3], [4], [5], [6], [7]]. When harvesting larger samples during EBUS-IFB, 1.5- and 1.9-mm forceps have been used in place of miniforceps of 0.8–1.15 mm [[9], [10], [11]]. However, in 20 % of cases, 1.5-mm forceps could not be introduced into the lesion because of their larger size [9]. The 1.1-mm ultrathin cryoprobe used in these cases was adequately small, making insertion feasible. Furthermore, 2–3 cryo-passes were needed for a plateaued diagnostic yield with a 1.1-mm cryoprobe due to the heterogenicity of the LN structure [12]. In our DC method, the EBUS scope is not removed, and we are not required to reidentify the lesion. Each biopsy may allow a repeat biopsy to become more feasible. The procedure time of conventional EBUS-TBCB has been approximately 9.5 min for three cryobiopies [1,2]. We collected three and four cryobiopsy specimens in 2.2 and 3.0 min in Case 1, Case 2, respectively.

Cryobiopsy allows for sample size adjustment based on freezing time. Most previous prospective studies on conventional EBUS-TBCB have set freezing times at 3–7 s [[1], [2], [3], [4]], but the optimal time remains controversial. A longer freezing time prevents the cryobiopsy specimen from passing through the puncture tract. Shyang Kho et al. demonstrated that a 3.1–4 s freezing time was optimal [12]. In the DC method of TBLC, a short freezing time of 2–3 s with a 1.1-mm ultrathin cryoprobe is recommended to circumvent the size limitation of the 2.0-mm working channel of a thin bronchoscope [8]. In contrast, the 2.2-mm working channel of the EBUS scope was slightly larger than that of the thin bronchoscope; hence, activation up to the optimal 4 s could be achieved even by the DC method. We could collect up to a 6.5 mm² sample. The reported mean sample sizes obtained with 0.8-mm miniforceps, 1.9-mm forceps, and ultrathin cryoprope with 7 s freezing were 1.3, 2.1–3.5, and 8.1 mm², respectively [4,11]. Further studies are needed to determine the optimal freezing time and sample size for this method.

Bleeding is a critical problem with cryobiopsy. The major bleeding rate in TBLC (16.2 %) was significantly higher than that with forceps biopsy (4.2 %) [13]. The bleeding rate of conventional EBUS-TBCB is equivalent to that of EBUS-TBNA and IFB [[1], [2], [3], [4], [5], [6]], and the rate of grade 3–4 bleeding is 1–2 % [1,3,14]. However, to ensure a safe procedure, the inability to observe the bleeding site for several seconds should be avoided, and airway management such as endotracheal intubation must be considered [5]. The DC method allows the operator to remain near the biopsy site, and to immediately suction and apply hemostasis using an EBUS balloon. Therefore, the DC method can be performed more safely than the conventional EBUS-TBCB, even without intubation.

4. Conclusion

• •We developed a novel method for direct collection through a working channel in an EBUS-TBCB with 1.1-mm ultrathin cryoprobe.
• •We have performed non-intubated cryobiopsy with a freezing time up to 4 s without removal of the scope, allowing a safe and prompt procedure.
• •A prospective trial to assess the diagnostic yield, complication rate, procedure time, and cost-effectiveness of EBUS-IFB and conventional TBCB is necessary to further demonstrate that the DC method is an effective and safe procedure for EBUS-TBCB.

CRediT authorship contribution statement

Mikito Suzuki: Writing – review & editing, Writing – original draft, Visualization, Project administration, Data curation, Conceptualization. Kaito Yano: Writing – review & editing, Data curation. Tomohiro Imoto: Writing – review & editing, Data curation. Reiko Shimizu: Writing – review & editing, Data curation. Kazuo Nakagawa: Writing – review & editing, Supervision.

Formatting of funding sources

This study did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Handling Editor: DR AC Amit Chopra