Diagnostic accuracy and safety of 1.1-mm cryoprobe biopsy for peripheral pulmonary lesions with or without oversheath

Introduction

Background

Radial endobronchial ultrasound (R-EBUS)-guided forceps biopsy has traditionally been the primary method used for diagnosing peripheral pulmonary lesions (PPLs). Although diagnostic yields vary by institution and operator, a meta-analysis reported an overall yield of approximately 72% (1). Despite its widespread use in bronchoscopic procedures, forceps biopsy often provides limited specimen volume and is susceptible to crush artifacts, which can compromise histological and molecular diagnostic accuracy (2).

Compared with forceps biopsy, cryoprobe biopsy provides larger tissue samples and preserves tissue architecture more effectively, enabling more reliable histopathological evaluation (3). It has also demonstrated a higher tissue adequacy and improved diagnostic accuracy in cases of suspected lung cancer (4). Cryobiopsy specimens also provide larger quantities of nucleic acids for molecular analysis and demonstrate strong concordance in immunohistochemistry, including enhanced detection of programmed death-ligand 1 expression (5). Recent technological advancements have further reduced cryoprobe diameters from the conventional 1.9 mm models to 1.1 mm (6).

Rationale and knowledge gap

Despite its advantages, cryoprobe biopsy typically requires removal of the bronchoscope to retrieve samples, which can delay immediate management of potential complications such as bleeding. In addition, as targeting must be reestablished for each pass, biopsy reproducibility may be reduced, particularly when multiple samples are required (7,8).

The 1.1-mm cryoprobe can be used with or without an oversheath (Figure 1). The use of an oversheath allows continuous biopsy without removing the bronchoscope between samples, facilitating rapid re-advancement of the bronchoscope for bleeding control. However, specimens retrieved through an oversheath must pass through the working channel, which may limit tissue size compared with that via procedures performed without an oversheath (9). Furthermore, this approach requires a bronchoscope with a larger working channel (≥2.0 mm), potentially restricting its use in anatomically challenging airways.

Figure 1 Schematic illustration of a 1.1-mm cryoprobe used with an oversheath positioned within the bronchoscope working channel. The device shown is not fully advanced; in actual procedures, the oversheath can extend beyond the tip of the bronchoscope, allowing access to peripheral pulmonary lesions.

Although cryobiopsy is being increasingly adopted for diagnosing PPLs, evidence directly comparing the diagnostic performance and procedural safety of procedures performed with and without an oversheath remains limited. It remains unclear whether the use of an oversheath affects diagnostic yield while improving procedural safety, particularly for small peripheral lesions.

Objective

This study primarily aimed to determine whether the use of an oversheath influences diagnostic yield and procedural safety during a 1.1-mm cryoprobe biopsy for PPLs. It also aimed to identify factors associated with diagnostic success. We present this article in accordance with the STARD reporting checklist (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-1-0152/rc).

Methods

Study population

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of Severance Hospital (No. 4-2025-1509), and the requirement for informed consent was waived owing to the retrospective nature of the study.

A retrospective analysis was conducted in patients who underwent cryoprobe biopsy for lung lesions at Severance Hospital between March 1, 2022 and August 7, 2023.

Patients with peripheral lesions measuring ≤30 mm and suspected malignancy were analyzed. Consistent with established definitions, PPLs were defined as focal radiographic opacities that are not visible beyond the segmental bronchi on flexible bronchoscopy (10).

Only lesions with a positive bronchus sign on pre-procedural chest computed tomography (CT) were considered eligible for bronchoscopic biopsy and included in this study; therefore, all lesions in both groups were positive for bronchus sign.

Patients who underwent therapeutic procedures, had post-chemotherapy lesions, and underwent biopsies for interstitial lung disease were excluded.

Allocation to procedures performed with or without an oversheath was determined by the operator’s clinical judgment rather than by randomization. Peripheral lesions that could be accessed at an appropriate angle using the BF-1TQ290 bronchoscope and were technically feasible for oversheath insertion were assigned to the oversheath group. When bronchoscopic access was restricted or oversheath insertion was technically challenging owing to anatomical constraints, biopsies were performed without an oversheath. The choice of procedural approach was based on a comprehensive assessment of lesion location, bronchial angulation, and overall technical feasibility.

Procedures

All procedures were performed by a single experienced bronchoscopist under moderate sedation with intravenous midazolam and fentanyl.

A BF-P260F bronchoscope (Olympus, Tokyo, Japan) was used for procedures performed without an oversheath. A BF-1TQ290 bronchoscope (Olympus) was used; procedures were performed with an oversheath. The target bronchus was identified using pre-procedural CT.

In the with oversheath group, the oversheath was positioned in the target bronchi. The oversheath used with the 1.1-mm cryoprobe had a total length of 817 mm, which exceeded the working channel length of the BF-1TQ290 bronchoscope (approximately 700–740 mm), allowing it to extend approximately 6–8 cm beyond the tip of the bronchoscope when fully advanced. In both groups, the target lesion was localized using R-EBUS and fluoroscopy. R-EBUS findings were categorized as “within”, “adjacent”, or “marginal (not targeted)” according to conventional definitions.

After successful localization, transbronchial biopsy (TBB) was performed using forceps. Bleeding was initially managed with cold saline instillation and diluted epinephrine. In cases of persistent grade II or higher bleeding, a hemostatic balloon (B5-2C; Olympus) was additionally applied. Hemostasis was achieved after each forcep biopsy using these measures, and cryobiopsy was subsequently performed.

In the with oversheath group, freezing was done for 2–3 s compared with 6–8 seconds in the without oversheath group. The freezing duration was determined at the operator’s discretion, who took into account procedural conditions and adequacy of the specimen.

A chest radiograph was obtained immediately following the procedure to assess for pneumothorax, and a follow-up chest radiograph was performed at 6:00 a.m. the following morning to detect any delayed pneumothorax.

Diagnosis

A diagnosis was considered successful if the biopsy identified a malignancy or a specific benign condition, such as pulmonary tuberculosis or fungal infection. Non-specific benign findings were not regarded as diagnostic, even if supported by subsequent radiological follow-up, in accordance with contemporary consensus recommendations (11).

Diagnostic failure was defined as failure of both the initial and any subsequent TBB procedures to identify a malignancy or specific disease. In such cases, a final diagnosis was confirmed using alternative methods such as surgical biopsy or CT-guided transthoracic needle biopsy (12). Additionally, cases in which no additional biopsy procedures were performed were classified as diagnostic failures if the follow-up chest CT scan obtained after 3 months demonstrated no interval change or lesion progression.

This composite reference standard was chosen because surgical pathology is not routinely available for all PPLs and long-term radiological follow-up is an accepted alternative standard for confirmation of benign disease in real-world clinical practice.

Statistical analysis

All statistical analyses were performed using R software (R Foundation for Statistical Computing, Vienna, Austria; version 4.2.3). Continuous variables with a normal distribution were compared using Student’s t-test. Continuous or ordinal variables with non-normal distributions were analyzed using the Mann-Whitney U test.

Categorical variables were compared using chi-squared or Fisher’s exact tests, as appropriate. Comparisons of diagnostic yield and complication rates (grade II–III bleeding and pneumothorax) were performed exclusively with Fisher’s exact test because of the small number of events.

Univariable logistic regression was employed to identify variables associated with diagnostic success. Variables with statistical significance were subsequently entered into a multivariable logistic regression model using stepwise selection based on Akaike’s Information Criterion. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) and corresponding P values were reported. All tests were two-sided, and a P value of <0.05 was considered significant. All analyses were performed on a complete-case basis, and no imputation was performed for missing data.

Results

Patient and lesion characteristics

Between March 1, 2022 and August 7, 2023, 324 cryobiopsies for lung lesions were performed at our center using a 1.1-mm cryoprobe. After applying the predefined inclusion and exclusion criteria, 239 patients were excluded, resulting in 85 eligible patients for analysis. Among these, 39 procedures were performed with an oversheath and 46 without an oversheath (Figure 2).

Figure 2 Flow diagram depicting the patient selection process, application of exclusion criteria, and allocation to cryobiopsy performed with or without an oversheath.

There were no significant differences in baseline demographic and lesion characteristics, including age, sex, lesion size, lesion location, and radiological features, between the two groups (Table 1). The mean lesion sizes were 21.4 mm in the with oversheath group and 20.3 mm in the without oversheath group (21.4±5.6 vs. 20.3±6.8 mm; P=0.42). Lesions in the right lower lobe bronchus were more frequent in the without oversheath group (32.6% vs. 17.9%, P=0.30).

However, the R-EBUS position differed significantly between the two groups. A “within” R-EBUS position was achieved more frequently in procedures performed with an oversheath (71.8% vs. 41.3%; P=0.01), whereas “adjacent” or “marginal” positions were more common in the without oversheath group.

With regard to the biopsy technique, the oversheath group underwent fewer forceps biopsies (median, 4 vs. 7) but a greater number of cryobiopsies (median, 4 vs. 2), indicating the advantage of performing repeated cryobiopsies without withdrawing the bronchoscope.

Diagnostic yield

The overall diagnostic success rate of the 85 patients was 76.5% (Table 2). Lesion size was a significant determinant of diagnostic yield: lesions measuring >20 mm had a diagnostic yield of 87.0%, whereas lesions measuring ≤20 mm had a yield of 64.1% (P=0.03). A higher diagnostic yield of cryobiopsy was observed in lesions >20 mm compared with lesions ≤20 mm (80.4% vs. 59.0%); however, the difference was not statistically significant (P=0.054). Cryobiopsy demonstrated a substantially higher diagnostic yield compared with that via forceps biopsy (70.6% vs. 39.2%, Table 2). Overall, in 39.2% of cases, diagnosis was established exclusively by cryobiopsy compared with 6.8% cases using forceps biopsy alone. This difference was observed in lesions measuring 21–30 mm (47.6% vs. 7.1%, P<0.001) and those measuring ≤20 mm (28.1% vs. 6.2%, P=0.065, Figure 3).

Figure 3 Comparison of exclusive diagnostic yield between cryobiopsy and forceps biopsy according to lesion size.

The use of an oversheath was associated with a higher overall diagnostic success rate compared with that via procedures performed without an oversheath (84.6% vs. 69.6%, OR: 2.41; 95% CI: 0.85–7.51), although the difference was not significant (P=0.11) (Table 3). This effect was more pronounced for lesions ≤20 mm, with diagnostic yields of 80.0% in the with oversheath group and 54.2% in the without oversheath group, respectively (P=0.11). For lesions measuring 21–30 mm, the diagnostic yields were similarly high in both groups (87.5% vs. 86.4%).

Final diagnosis

The distribution of final diagnosis is summarized in Table 4. Lung adenocarcinoma was the most common diagnosis in both groups, accounting for 66.7% in the with oversheath group and 50.0% in the without oversheath group. Benign lung diseases—including pneumonia, cryptococcosis, nontuberculous mycobacterial infection, and tuberculosis—were identified in three patients in both groups. Metastatic lung malignancy was observed in one patient in the with oversheath group and in four patients in the without oversheath group. Additionally, one patient with mucoepidermoid carcinoma was classified as having a malignant lesion.

Among non-diagnostic procedures, subsequent diagnoses included lung adenocarcinoma, small-cell lung cancer, metastatic malignancy, and benign lung disease. Additionally, three patients in the without oversheath group were classified as having rule-out lung cancer based on radiologic suspicion, without pathologic confirmation.

Predictors of diagnostic success

In the univariable logistic regression analysis, lesion size and R-EBUS position were significantly associated with diagnostic success. Lesions >20 mm were associated with higher odds of a diagnosis compared with lesions ≤20 mm (OR: 3.73, 95% CI: 1.32–11.74, P=0.02). Similarly, a “within” R-EBUS position was associated with increased diagnostic success (OR: 5.48, 95% CI: 1.86–18.64, P=0.003). No other variables were significant in the univariable analysis (Table 5).

In the multivariable analysis, only a “within” R-EBUS position (adjusted OR: 4.30, 95% CI: 1.39–15.07, P=0.02) remained independently associated with diagnostic success. Oversheath use demonstrated a positive but non-significant association with diagnostic success.

Complications

Mild bleeding was common in both groups and occurred in 74.4% of procedures with an oversheath and 50.0% of procedures without an oversheath (Table 1). Moderate-to-severe bleeding (grades II–III) was less frequent in the with oversheath group (25.6% vs. 50.0%, P=0.03, Table 6). Accordingly, a hemostatic balloon was applied in 10 cases (25.6%) in the with oversheath group and 23 cases (50.0%) in the without oversheath group. No grade III bleeding events occurred in the with oversheath group, whereas one patient (2.2%) in the without oversheath group required aggressive management.

No pneumothorax occurred in either group, despite the inclusion of peripheral and cryobiopsy lesions.

Discussion

This study evaluated the impact of oversheath use and predictors of diagnostic success in cryobiopsies of PPLs performed using a 1.1-mm cryoprobe. Overall, cryobiopsy demonstrated a higher diagnostic yield than forceps biopsy (70.6% vs. 39.2%). Although oversheath use was not independently associated with diagnostic success in multivariable analysis, the use of an oversheath did not compromise diagnostic performance. Importantly, oversheath-assisted procedures were associated with a significantly lower incidence of moderate-to-severe bleeding compared with procedures performed without an oversheath (25.6% vs. 50.0%, P=0.03). These findings suggested that oversheath use may provide a procedural safety advantage during cryobiopsy while maintaining diagnostic performance.

Several factors may account for the lower diagnostic yield observed in procedures performed without an oversheath. This group had a higher proportion of subsolid nodules on CT (60.9% vs. 43.6%), a radiological feature known to reduce bronchoscopic diagnostic performance (13). Subsolid lesions are also associated with a lower probability of achieving a “within” R-EBUS position compared with solid lesions, which might have contributed to the observed imbalance in R-EBUS positioning between the two groups. Moreover, the use of an oversheath likely enhances procedural reproducibility. Similar to the stabilizing effect of a guide sheath, an oversheath helps maintain the biopsy channel and enables more consistent targeting of the lesion (14).

Across all procedures, the overall diagnostic success rate was 76.5%, which exceeds the diagnostic yields (approximately 70–72%) historically reported for forceps biopsy alone in PPLs (15), and is comparable to the yields reported when forceps and cryoprobe biopsies are combined (6). Cryobiopsy demonstrated a markedly higher diagnostic yield compared with that via forceps biopsy, with 39.2% of diagnoses established exclusively by cryobiopsy compared with only 6.8% by forceps biopsy alone. In the present study, the diagnostic yield of forceps biopsy was approximately 45%, which is lower than previously reported yields of 33–46% for lesions ≤20 mm and 58.7% for lesions ≤30 mm (15,16). This discrepancy may reflect the limited number of forceps samples obtained, given that cryobiopsy was performed concurrently and in the absence of a guide sheath, reflecting a real-world setting in which forceps performance may be suboptimal.

Lesion size and R-EBUS findings have been reported as important determinants of bronchoscopic diagnostic yield in previous studies (16-18). In our study, smaller lesions tended to show lower diagnostic yields, although this did not reach statistical significance, whereas a “within” R-EBUS position was significantly associated with improved diagnostic success.

In the subgroup of lesions ≤20 mm, a higher diagnostic yield was observed in the with oversheath group. This finding may suggest a potential benefit of oversheath use in small PPLs when the target bronchus is accessible; however, this should be interpreted with caution, given the limited sample size and potential selection bias.

From a safety perspective, oversheath use was associated with a significantly lower incidence of moderate-to-severe bleeding complications. No grade III bleeding events occurred in the with oversheath group, whereas one such event was reported in the without oversheath group. This safety benefit is likely attributable to the ability to achieve immediate hemostasis without removing the bronchoscope as well as the shorter freezing times typically employed during oversheath-assisted cryobiopsy. Although smaller lesions tended to be associated with more frequent bleeding events (Table S1), this difference was not significant, which could be due to the limited sample size. Importantly, pneumothorax did not occur in either group despite all lesions being peripheral and cryobiopsy being performed, supporting the safety of the 1.1-mm cryoprobe when applied with an appropriate technique (19). This favorable safety profile may also reflect the use of fluoroscopic guidance and the fact that all procedures were performed by a single experienced bronchoscopist.

Limitations and future directions

This study has several limitations. First, it was a single-center retrospective study with a limited sample size, and the decision to use an oversheath was determined by the operator rather than by randomization, introducing potential selection bias. In addition, oversheath use was primarily applied to lesions that were anatomically accessible with the BF-1TQ290 bronchoscope, which may have influenced the observed diagnostic performance. In our cohort, procedures performed with an oversheath more frequently achieved a “within” R-EBUS position (71.8% vs. 41.3%), which may partly reflect differences in bronchoscopic accessibility between the two groups.

Furthermore, differences in lesion characteristics between the groups could have influenced the results. In our cohort, the without oversheath group included a higher proportion of subsolid nodules [28/46 (60.9%) vs. 17/39 (43.6%)], which are known to be associated with lower bronchoscopic diagnostic yield (13). Therefore, differences in lesion characteristics may have contributed to differences in R-EBUS positioning between the two groups, and the findings should be interpreted with caution.

Second, potential differences in specimen quality related to oversheath use, such as tissue size, preservation, or suitability for molecular testing, were not evaluated in this study. Future multicenter prospective studies with larger cohorts are needed to validate these findings and to assess specimen quality metrics associated with oversheath-assisted cryobiopsy.

Conclusions

Cryobiopsy using a 1.1-mm cryoprobe provides high-quality tissue acquisition for the diagnosis of PPLs, overcoming some of the limitations of conventional forceps biopsy. Oversheath-assisted cryobiopsy was associated with improved procedural safety, particularly in reducing moderate-to-severe bleeding events. Although a higher diagnostic yield was observed in certain subgroups, oversheath use was not independently associated with diagnostic success, suggesting that its primary benefit lies in procedural stability and safety rather than diagnostic enhancement. Achieving a “within” position on R-EBUS was a key determinant of diagnostic success, emphasizing the importance of accurate lesion localization. Therefore, a combined approach using both forceps biopsy and cryobiopsy may optimize overall diagnostic performance.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STARD reporting checklist. Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-1-0152/rc

Data Sharing Statement: Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-1-0152/dss

Peer Review File: Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-1-0152/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-1-0152/coif). The 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. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of Severance Hospital (No. 4-2025-1509), and the requirement for informed consent was waived owing 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. Sryma PB, Mittal S, Madan NK, et al. Efficacy of Radial Endobronchial Ultrasound (R-EBUS) guided transbronchial cryobiopsy for peripheral pulmonary lesions (PPL...s): A systematic review and meta-analysis. Pulmonology 2023;29:50-64. [Crossref] [PubMed]
2. Kinoshita K, Morikawa K, Tsuruoka H, et al. Efficacy of combined transbronchial lung cryobiopsy and conventional forceps biopsy for lung malignancies: a prospective cohort study. Sci Rep 2023;13:1850. [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. Hetzel J, Eberhardt R, Herth FJ, et al. Cryobiopsy increases the diagnostic yield of endobronchial biopsy: a multicentre trial. Eur Respir J 2012;39:685-90. [Crossref] [PubMed]
5. 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]
6. Kim SH, Mok J, Jo EJ, et al. The Additive Impact of Transbronchial Cryobiopsy Using a 1.1-mm Diameter Cryoprobe on Conventional Biopsy for Peripheral Lung Nodules. Cancer Res Treat 2023;55:506-12. [Crossref] [PubMed]
7. 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]
8. DiBardino DM, Haas AR, Lanfranco AR, et al. High Complication Rate after Introduction of Transbronchial Cryobiopsy into Clinical Practice at an Academic Medical Center. Ann Am Thorac Soc 2017;14:851-7. [Crossref] [PubMed]
9. Maldonado F, Danoff SK, Wells AU, et al. Transbronchial Cryobiopsy for the Diagnosis of Interstitial Lung Diseases: CHEST Guideline and Expert Panel Report. Chest 2020;157:1030-42. [Crossref] [PubMed]
10. Mondoni M, Sotgiu G, Bonifazi M, et al. Transbronchial needle aspiration in peripheral pulmonary lesions: a systematic review and meta-analysis. Eur Respir J 2016;48:196-204. [Crossref] [PubMed]
11. Gonzalez AV, Silvestri GA, Korevaar DA, et al. Assessment of Advanced Diagnostic Bronchoscopy Outcomes for Peripheral Lung Lesions: A Delphi Consensus Definition of Diagnostic Yield and Recommendations for Patient-centered Study Designs. An Official American Thoracic Society/American College of Chest Physicians Research Statement. Am J Respir Crit Care Med 2024;209:634-46.
12. Wang J, Zhang T, Xu Y, et al. Comparison between percutaneous transthoracic co-axial needle CT-guided biopsy and transbronchial lung biopsy for the diagnosis of persistent pulmonary consolidation. Insights Imaging 2023;14:80. [Crossref] [PubMed]
13. Matsumoto Y, Kho SS, Furuse H. Improving diagnostic strategies in bronchoscopy for peripheral pulmonary lesions. Expert Rev Respir Med 2024;18:581-95. [Crossref] [PubMed]
14. Chung C, Kim Y, Lee JE, et al. Diagnostic Value of Transbronchial Lung Cryobiopsy Using an Ultrathin Cryoprobe and Guide Sheath for Peripheral Pulmonary Lesions. J Bronchology Interv Pulmonol 2024;31:13-22. [Crossref] [PubMed]
15. Schreiber G, McCrory DC. Performance characteristics of different modalities for diagnosis of suspected lung cancer: summary of published evidence. Chest 2003;123:115S-28S.
16. Eberhardt R, Ernst A, Herth FJ. Ultrasound-guided transbronchial biopsy of solitary pulmonary nodules less than 20 mm. Eur Respir J 2009;34:1284-7. [Crossref] [PubMed]
17. Yamada N, Yamazaki K, Kurimoto N, et al. Factors related to diagnostic yield of transbronchial biopsy using endobronchial ultrasonography with a guide sheath in small peripheral pulmonary lesions. Chest 2007;132:603-8. [Crossref] [PubMed]
18. Ali MS, Trick W, Mba BI, et al. Radial endobronchial ultrasound for the diagnosis of peripheral pulmonary lesions: A systematic review and meta-analysis. Respirology 2017;22:443-53. [Crossref] [PubMed]
19. Thiboutot J, Illei PB, Maldonado F, et al. Safety and Feasibility of a Sheath Cryoprobe for Bronchoscopic Transbronchial Biopsy: The FROSTBITE Trial. Respiration 2022;101:1131-8. [Crossref] [PubMed]