Feasibility of direct cryobiopsy specimen retrieval through the working channel of an ultrathin bronchoscope—a retrospective study of single institute

Background: Cryobiopsy method using direct specimen retrieval through the working channel of the bronchoscope has recently been reported as a diagnostic option. However, its feasibility using an ultrathin bronchoscope (UTB) with 1.7-mm working channel has not been investigated. The aim of this study was to evaluate the feasibility, diagnostic yield, specimen size, and safety of direct cryobiopsy specimen retrieval through the 1.7-mm working channel of an UTB.

Methods: We retrospectively reviewed patients with peripheral lesions who underwent cryobiopsy with direct specimen retrieval through the working channel using an UTB at National Hospital Organization (NHO) Okayama Medical Center between November 2022 and December 2025. We compared specimens obtained by cryobiopsy and small forceps biopsy. Diagnostic yield, and procedural safety were also evaluated.

Results: Eighteen patients were included. We evaluated 53 cryobiopsy specimens and 18 forceps biopsy specimens. The median lesion diameter was 13.5 mm (range, 10–28 mm). Cryobiopsy specimens were significantly larger than forceps specimens (1.97 vs. 1.00 mm², P<0.001). The overall diagnostic yield was 72.2% (13 of 18). Bleeding severity was Grade 0 in 15 cases and Grade 1 in three cases, and hemostasis was achieved with suction with UTB alone in all cases. No pneumothorax or severe complications occurred, although pinhole damage to the bronchoscope working channel was observed in one case (freezing time, 4 seconds).

Conclusions: Direct cryobiopsy specimen retrieval through a 1.7-mm working channel of an UTB provides larger specimens than small forceps biopsy. This technique may improve diagnostic yield for peripheral pulmonary lesions, although caution is required regarding potential bronchoscope damage with longer freezing times.