Evaluation of 1.1 mm ultrathin cryobiopsy through a guide sheath for sampling of peripheral pulmonary lesions

Introduction

Widespread adoption of low-dose computed tomography (CT) has improved the detection and diagnostic rates of peripheral pulmonary lesions (PPLs) (1). However, achieving minimally invasive diagnosis of these lesions remains challenging. Over the past decade, bronchoscopic diagnostic rates have improved through the integration of radial endobronchial ultrasound (R-EBUS) and virtual bronchoscopy navigation. Recent studies of endobronchial ultrasound with a guide sheath (EBUS-GS) show that R-EBUS with guide-sheath (GS) achieves a higher tissue diagnosis rate (55.3%) compared to procedures without GS (46.6%) (2).

Although forceps are commonly used for tissue sampling, this method often damages small specimens. Cryobiopsy is an alternative approach that uses a gas-cooled probe tip to freeze and extract larger, higher-quality tissue samples (3). This technique has demonstrated effectiveness in diagnosing bronchial tumors and interstitial lung diseases (4-11). However, cryoprobe biopsy can lead to serious complications, including severe bleeding and pneumothorax (5). Various risk-mitigation strategies have been developed, such as balloon occlusion and double-scope methods under intubation (4,8). 1.9 or 2.4 mm cryoprobe biopsy requires intubation and complete bronchoscopic removal to prevent channel damage.

The 1.1 mm ultra-thin cryoprobe offers the advantage of passing through a large GS, allowing biopsy without intubation and requiring only channel manipulation. In addition, its combination with GS may improve diagnostic rates. This study aims to retrospectively evaluate the safety and efficacy of ultrathin cryobiopsy through a guide-sheath performed under R-EBUS guidance at our institution. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1711/rc).

Methods

Study design and patient population

This study was a retrospective observational study conducted at The Fraternity Memorial Hospital. We reviewed patients who underwent bronchoscopy using a large-diameter bronchoscope and a large guide sheath for evaluation of PPLs between January 2022 and May 2023. Various types of PPLs were indicated, including solid lesions, pulmonary infiltration, and ground-glass opacities. The decision to perform either ultrathin cryobiopsy through a guide-sheath (GS-UTCB) or conventional EBUS-GS procedure biopsy (Bx) was made at the discretion of the bronchoscopist.

Clinical and procedural data, including bronchoscopic parameters such as examination time and procedure-related adverse events, were retrospectively collected from electronic medical records and archived procedural video recordings. These parameters were then compared between GS-UTCB group and Bx group. Additionally, pathological specimens obtained from GS-UTCB group underwent detailed analysis, including assessments of diagnostic yield, tissue area, and the degree of crush artefacts. This study was conducted in accordance with the principles of the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of Fraternity Memorial Hospital (approval No. 304). Written informed consent was waived due to the retrospective nature of the study.

Bronchoscopy procedures

All bronchoscopies were performed under moderate-to-deep sedation using a combination of opioids and sedatives. The procedures utilized a large-diameter bronchoscope (1TQ290 or 1TH1200; Olympus, Tokyo, Japan) with a 6.1 mm outer diameter and 3.0 mm working channel. R-EBUS findings were categorized as within, adjacent to, or invisible according to the positional relationship between the probe and target PPL, as follows: within, abnormal echogenicity of the entire examined circumference; adjacent to, abnormal echogenicity of part of the examined circumference; and invisible, normal lung parenchymal echogenicity (5). Blizzard signs were also categorized in the R-EBUS findings as follows ; blizzard sign, a subtle but noticeable increase in the intensity and radius of whitish acoustic shadow when scanning from normal lung tissue to ground-glass areas (12). After localizing the target lesion under X-ray fluoroscopy and R-EBUS guidance, a conventional EBUS-GS procedure was performed using standard forceps (1.9 mm diameter) through a large GS (SG-201C, Olympus, Tokyo, Japan), with 3–5 biopsies obtained. Subsequently, a single-use 1.1 mm cryoprobe (length 1,150 mm, Erbe Elektromedizin GmbH, Tübingen, Germany) was inserted into the GS. The cryoprobe was extended approximately 15 mm from the tip of the GS (Figure 1). After freezing for 2 to 5 seconds, the cryoprobe alone was withdrawn while leaving the GS in place. Unlike conventional cryobiopsy methods that require endotracheal intubation, this procedure was performed without intubation. The probe tip was then thawed with saline, and the retrieved tissue samples were preserved in separate formalin containers. When specimens could not be obtained, we adjusted the depth of the biopsy site or changed to a nearby bronchus for sampling. A pathologist independently evaluated the histological specimens obtained from both the standard forceps biopsy and cryobiopsy procedures.

Figure 1 1.1 mm ultrathin cryoprobe procedure. (A) 1.1 mm ultrathin cryoprobe can be passed through the guide sheath. (B) Guide sheath with an inserted cryoprobe is inserted into the working channel of the bronchoscope for use.

Bronchoscopic parameters

As defined in the study design, bronchoscopic parameters were compared between GS-UTCB group and Bx group. These included total examination time, device-specific biopsy time, and procedure-related safety outcomes. All data were collected retrospectively from electronic medical records and archived bronchoscopy video recordings.

Examination time was defined as the interval from bronchoscope insertion to completion of all procedures and removal of the bronchoscope. The standard forceps biopsy time was measured from insertion of the R-EBUS with GS until completion of the forceps biopsy procedure. The 1.1 mm cryoprobe biopsy time was measured from completion of the forceps biopsy to the end of the cryoprobe biopsy procedure. Safety was assessed based on adverse events occurring during or after bronchoscopy.

In accordance with the standardized definition of bleeding (13), hemorrhage was graded as follows: grade 0, no bleeding; grade 1, blood suctioning required for <1 min; grade 2, suctioning required for >1 min, repeat wedging of the bronchoscope for persistent bleeding or the application of cold saline, diluted vasoactive substances, or thrombin required; grade 3, selective intubation needed for <20 min; grade 4, persistent selective intubation or emergency care required (i.e., life-threatening complications).

Additional clinical factors were also collected, including age, sex, smoking status, use of anticoagulant or antiplatelet medications, lesion morphology and location (lobe), and the presence of the bronchus sign.

Diagnostics and pathologic analysis in GS-UTCB group

In the GS-UTCB group, we analyzed the diagnostic yield of both the 1.1 mm cryoprobe and standard forceps. Additionally, tissue area and crush artifacts were evaluated for each device. The diagnostic yield for each device was calculated by dividing the number of patients with a positive diagnosis by the total number of GS-UTCB procedures. Patients were considered non-diagnostic when no definitive pathological diagnosis could be obtained from either forceps biopsy or cryobiopsy. Patients were considered diagnosed if they showed either malignant lesions with positive pathological features or benign lesions with specific pathological features, sometimes supplemented with bacterial or mycobacterial culture data.

The tissue area from each device was calculated using cellSens imaging software (Evident, Tokyo, Japan) under 40× total magnification. Crush artifacts were categorized into three categories: mild, when the crush cell area was less than 30% of the total specimen area; moderate, when more 30% was affected but diagnostics were available; and severe, when more than 30% was affected and a diagnosis was not possible. Cush artifacts were assessed by the same pathologists who diagnosed the cases.

Statistical analysis

Baseline patient characteristics were compared between the two groups using the chi-square test. Safety comparisons between the GS-UTCB and Bx groups were performed using the Fisher’s exact test. A P value <0.05 was considered statistically significant. Examination times and pathological areas were analyzed using a two-tailed Mann-Whitney U test. A P value <0.05 was considered statistically significant. All statistical analyses were performed using EZR software version 1.61 (Jichi Medical University Saitama Medical Center, Japan).

Results

Patient characteristics

A flowchart of the study is shown in Figure 2. Of the 109 selected patients, 48 patients were included in the analysis: 13 in the GS-UTCB group and 34 in the Bx group. Baseline patient characteristics are shown in Table 1. There were no significant differences in background factors between the groups. The lesion types were distributed in the GS-UTCB/Bx group, as follows: solid lesions (61.5%/70.5%), pulmonary infiltration (15.4%/17.1%), and ground-glass opacities (23.1%/11.4%). Lesions were predominantly located in the right and left upper lobes in the GS-UTCB group (69.2%), whereas more lesions were located in the right and left lower lobes in the Bx group (41.2%).

Figure 2 Flow diagram illustrating patient selection. Bx, conventional EBUS-GS procedure; EBUS, endobronchial ultrasound; GS, guide sheath; GS-UTCB, ultrathin cryobiopsy through a guide sheath.

Diagnostic yields

Final diagnostic yields obtained by standard forceps and 1.1mm cryoprobe in the GS-UTCB group are shown in Table 2. The diagnostic yield reached 92.3% in total, with 1.1 mm cryoprobe biopsy achieving 84.6% and standard forceps biopsy achieving 69.2%. This study included 9 benign diseases, and 4 malignant diseases. In benign diseases, the diagnostic yield reached 88.9% in total, with 1.1 mm cryoprobe biopsy achieving 88.9% and standard forceps biopsy achieving 66.7%. In malignant diseases, the diagnostic yield reached 100% in total, with 1.1 mm cryoprobe biopsy achieving 75% and standard forceps biopsy achieving 75%. One case of recurrent diffuse large B-cell lymphoma was diagnosed only by GS-UTCB (Figure 3). Diagnostic yields obtained by standard forceps in the Bx group are shown in Table 3. Total diagnostic yields in Bx group was 78%. The GS-UTCB group showed higher diagnostic yields than the Bx group.

Figure 3 Representative case. (A) A 70-year-old man presented with chest CT finding of multiple GGOs in the right middle and lower lobes. (B) R-EBUS findings revealed a Blizzard sign. (C) GS-UTCB was performed. 1.1 mm cryoprobe is inserted and specimen is retrieved through the GS. (D) 1.1 mm cryoprobe biopsy specimens. Clusters of cells with large nuclei are present in the alveoli (HE, ×10). (E) 1.1 mm cryoprobe biopsy specimens in high power field. It was stained positive by CD20 immunostains (×40). (F) Standard forceps specimen. It was difficult to diagnose because it was crushed with standard forceps. The patient was diagnosed recurrent diffuse large B-cell lymphoma only by GS-UTCB (HE, ×10). CT, computed tomography; GGO, ground glass opacity; GS-UTCB, ultrathin cryobiopsy through a guide sheath; R-EBUS, radial endobronchial ultrasound.

Procedure time comparison between the two groups

The procedure time results are shown in Table 4. The GS-UTCB group had a longer median procedure time (26.5 min) than the GS-UTCB group (23.0 min) (P=0.04). We compared the individual device-specific examination times in the GS-UTCB group. The median examination time was 7 min for the 1.1 mm cryoprobe and 5 min for the standard forceps; therefore, there was no significant difference between the devices.

Safety comparison between the two groups

The safety results are presented in Table 5. In the GS-UTCB group, grade 0 was 21.4%, grade 1 was 69.2%, grade 2 was 15.4%, and grade 3/4 was none. In the Bx group, grade 0 was 67.6%, and grade 1 was 26.5%, grade 2 was 5.9%. In this report, it seems that bleeding was more frequent with GS-UTCB group than Bx group. No severe or life-threatening bleeding and additional complications such as pneumothorax, myocardial infarction, air embolism, bronchoscopic damage were observed in both groups.

Specimen analysis in the GS-UTCB group

The cryoprobe yielded a significantly larger median tissue area [2.53 mm²; 95% confidence interval (CI): 1.07–10.79] than forceps [0.90 mm² (95% CI: 0.27–2.16), P<0.001] (Figure 4). Mild crush artifacts were found in 92.8% of cryoprobe samples vs. 64.2% in forceps; moderate and severe artifacts were more common in forceps samples.

Figure 4 Comparison of tissue area per device in GS-UTCB group. Tissue areas are presented as mm² with 95% confidence intervals. Pathological areas were analyzed using two-tailed Mann-Whitney U tests. A P value <0.05 was considered statistically significant. GS-UTCB, ultrathin cryobiopsy through a guide sheath.

Discussion

Previous studies have mainly described either extraction with the GS together, or the use of an ultrathin bronchoscope with a 1.1 mm cryoprobe for extraction (14). Few studies have reported performing biopsies while maintaining the position of the GS, likely due to concerns about sample retrieval through the GS or potential tissue retention within the GS (15-17). In our study, we obtained well-tolerated results by retrieving the 1.1 mm cryoprobe while maintaining the guide sheath in position. Although GS-UTCB required a longer examination time compared to EBUS-GS, the difference was only a few minutes and would not be problematic in daily clinical practice. R-EBUS procedure was performed in all cases, resulting in only one Invisible finding. This may be because we assessed findings such as the blizzard sign, resulting in fewer invisible findings.

In terms of safety, Previous studies of 1.9 mm cryoprobe biopsies reported mild bleeding in 39.3–56.5% of cases, moderate bleeding in 15–38.9% and severe bleeding in 1.1–1.2% (4-6,8,18). In our GS-UTCB group, mild bleeding occurred in 69.2%, moderate bleeding in 15.4%, and no severe bleeding was observed, which was comparative with previous reports. Additionally, the GS-UTCB group showed no other clinically significant adverse events.

In terms of diagnostic yield, in GS-UTCB group, standard forceps biopsy achieved 69.2%, which increased to 92.3% with the addition of 1.1 mm cryobiopsy. The 1.1 mm cryoprobe showed excellent results for both benign and malignant diseases, probably because of enough amounts of specimens with minimal crushing. Specimen size obtained using the 1.1 mm cryoprobe was 2.53 mm², and significantly larger than that of specimens obtained using standard forceps. Although the specimen size was smaller compared to previous reports using 1.9 mm probes (10,14,19), we believe that comparable diagnostic ability achieved through the combined use of R-EBUS. Our analysis of specimen crush artifacts showed less crushing in the GS-UTCB group. This reduction in crushing may improve diagnostic rates, particularly for conditions such as interstitial lung diseases and malignant lymphoma, which are traditionally difficult to diagnose with forceps biopsy (20), by allowing for better morphological and immunohistochemical staining analysis. Especially, one case of recurrent malignant lymphoma was successfully diagnosed only by GS-UTCB. GS-UTCB appeared to be more advantageous for diagnosis even in ground-glass opacity among malignant diseases, consistent with previous reports (21).

Previous research using 1.9 mm cryoprobe biopsies showed significantly higher diagnostic yields for non-upper lobe lesions compared to upper lesions (5). In our study, the diagnostic yield was tolerable including upper lobe lesions, and GS-UTCB may allow better access to upper lobe lesions, potentially overcoming previously identified challenges.

This study has several limitations. First, it was a single-center, retrospective observational study with a limited sample size, which may have introduced selection bias and limited the generalizability of the findings. Second, the allocation of patients to either the GS-UTCB or conventional EBUS-GS group was determined at the discretion of the bronchoscopist. In the GS-UTCB group, no invisible findings were observed. it was performed in cases where R-EBUS findings were obtained. Third, certain parameters such as bleeding severity and crush artifact grading involved subjective assessments, which could introduce observer bias.

The safety and diagnostic efficacy of GS-UTCB should be validated in larger, multicenter, prospective cohorts in future studies. Randomization should be applied to control for confounding factors such as lesion location and bronchoscope device selection in order to improve causal inference. Furthermore, investigating the efficacy of GS-UTCB in patient groups where large-bore bronchoscopy is difficult would improve the usefulness of this technique. Further investigation into the histopathological advantages of cryobiopsy, particularly for interstitial lung diseases or lymphoproliferative disorders, is also required.

Conclusions

GS-UTCB represents a safe and effective method for sampling of various types of PPLs, demonstrating the potential to complement conventional forceps biopsy with superior tissue quality and diagnostic capability. Future multicenter prospective studies would be preferable.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1711/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1711/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1711/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1711/coif). S.S. reports honoraria from Olympus and AMCO Inc. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the principles of the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of Fraternity Memorial Hospital (approval No. 304). Written informed consent was waived due to the retrospective nature of the study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. de Koning HJ, van der Aalst CM, de Jong PA, et al. Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial. N Engl J Med 2020;382:503-13. [Crossref] [PubMed]
2. Oki M, Saka H, Imabayashi T, et al. Guide sheath versus non-guide sheath method for endobronchial ultrasound-guided biopsy of peripheral pulmonary lesions: a multicentre randomised trial. Eur Respir J 2022;59:2101678. [Crossref] [PubMed]
3. Hetzel J, Hetzel M, Hasel C, et al. Old meets modern: the use of traditional cryoprobes in the age of molecular biology. Respiration 2008;76:193-7. [Crossref] [PubMed]
4. Nakai T, Watanabe T, Kaimi Y, et al. Safety profile and risk factors for bleeding in transbronchial cryobiopsy using a two-scope technique for peripheral pulmonary lesions. BMC Pulm Med 2022;22:20. [Crossref] [PubMed]
5. Matsumoto Y, Nakai T, Tanaka M, et al. Diagnostic Outcomes and Safety of Cryobiopsy Added to Conventional Sampling Methods: An Observational Study. Chest 2021;160:1890-901. [Crossref] [PubMed]
6. Jiang L, Xu J, Liu C, et al. Diagnosis of Peripheral Pulmonary Lesions with Transbronchial Lung Cryobiopsy by Guide Sheath and Radial Endobronchial Ultrasonography: A Prospective Control Study. Can Respir J 2021;2021:6947037. [Crossref] [PubMed]
7. Zhou G, Ren Y, Li J, et al. The effect of 1.9-mm versus 2.4-mm probes in transbronchial cryobiopsies for interstitial lung diseases: a prospective analysis. Ann Transl Med 2021;9:20. [Crossref] [PubMed]
8. Hetzel J, Wells AU, Costabel U, et al. Transbronchial cryobiopsy increases diagnostic confidence in interstitial lung disease: a prospective multicentre trial. Eur Respir J 2020;56:1901520. [Crossref] [PubMed]
9. Imabayashi T, Uchino J, Yoshimura A, et al. Safety and Usefulness of Cryobiopsy and Stamp Cytology for the Diagnosis of Peripheral Pulmonary Lesions. Cancers (Basel) 2019;11:410. [Crossref] [PubMed]
10. Nasu S, Okamoto N, Suzuki H, et al. Comparison of the Utilities of Cryobiopsy and Forceps Biopsy for Peripheral Lung Cancer. Anticancer Res 2019;39:5683-8. [Crossref] [PubMed]
11. Udagawa H, Kirita K, Naito T, et al. Feasibility and utility of transbronchial cryobiopsy in precision medicine for lung cancer: Prospective single-arm study. Cancer Sci 2020;111:2488-98. [Crossref] [PubMed]
12. Sasada S, Izumo T, Chavez C, et al. Blizzard Sign as a specific endobronchial ultrasound image for ground glass opacity: A case report. Respir Med Case Rep 2014;12:19-21. [Crossref] [PubMed]
13. Folch EE, Mahajan AK, Oberg CL, et al. Standardized Definitions of Bleeding After Transbronchial Lung Biopsy: A Delphi Consensus Statement From the Nashville Working Group. Chest 2020;158:393-400. [Crossref] [PubMed]
14. Schuhmann M, Bostanci K, Bugalho A, et al. Endobronchial ultrasound-guided cryobiopsies in peripheral pulmonary lesions: a feasibility study. Eur Respir J 2014;43:233-9. [Crossref] [PubMed]
15. Kho SS, Tan SH, Nyanti LE, et al. Feasibility of Cryobiopsy Specimen Retrieval Through Standard Guide Sheath for Peripheral Pulmonary Lesions Without Bronchoscope Removal. J Bronchology Interv Pulmonol 2024;31:e0982. [Crossref] [PubMed]
16. Herath S. Use of the 1.1 mm cryoprobe through the radial EBUS GS (without the need for a bronchial blocker) to obtain samples safely in diagnosing PPL. Respirol Case Rep 2023;11:e01128. [Crossref] [PubMed]
17. Kho SS, Chai CS, Nyanti LE, et al. Combination of 1.1 mm flexible cryoprobe with conventional guide sheath and therapeutic bronchoscope in biopsy of apical upper lobe solitary pulmonary nodule. BMC Pulm Med 2020;20:158. [Crossref] [PubMed]
18. Herth FJ, Mayer M, Thiboutot J, et al. Safety and Performance of Transbronchial Cryobiopsy for Parenchymal Lung Lesions. Chest 2021;160:1512-9. [Crossref] [PubMed]
19. Bian Y, Deng M, Gao Q, et al. The Diagnostic Efficiency and Safety of Transbronchial Lung Cryobiopsy Using 1.1-mm Cryoprobe in Diagnosing Interstitial Lung Disease. Lung 2024;202:615-23. [Crossref] [PubMed]
20. Nogawa H, Suzuki H, Ota H, et al. Transbronchial cryobiopsy using an ultrathin cryoprobe with a guide sheath for the diagnosis of pulmonary mucosa-associated lymphoid tissue lymphoma. J Thorac Dis 2023;15:7123-9. [Crossref] [PubMed]
21. Torky M, Elshimy WS, Ragab MA, et al. Endobronchial ultrasound guided transbronchial cryobiopsy versus forceps biopsy in peripheral lung lesions. Clin Respir J 2021;15:320-8. [Crossref] [PubMed]