• lung biopsy; diagnostic accuracy; complications;

Purpose
CT-guided percutaneous biopsy represents an essential element of the diagnostic algorithm of pulmonary nodules; moreover, mutation studies on specimens have become just as important as the diagnosis of cancer, due to the availability of targeted therapies.
The aims of this study were: to assess the diagnostic performance of 21-gauge needle for histologic and molecular characterization; to ascertain the complications rate of this procedure; to analyze patient/lesion/procedure-related factors influencing diagnosis and complications.

Materials and methods
We included 1111 patients (731 outpatient and 97 inpatient procedure) undergoing CT-guided pulmonary biopsy with 21-Gauge Chiba needle (January 2017- December 2021). No pathologist on-site was present.
Diagnostic results and complications were related to patient (emphysema, prior chest surgery/RT, supine/prone position), lesion (size, solid/subsolid, excavation/necrosis, fissures contact) and procedure parameters (breath-holding/freely breathing, muscle thickness, bone contact, needle-pleura angle, lesion-pleura distance).

Results
Cytologic specimens were obtained in 97,5% of patients and formalin fixed in 66,2%. 1026/1111 procedures were diagnostic (96,9% accuracy). Accuracy after re-biopsy (52 cases) was 96,5%. Only lesion size (>15 mm) correlated with diagnostic result. Specimens were adequate for molecular analysis in 94,6%. Complications occurred in about 43% of procedures including pneumothorax in 310 cases (27,9%) and bleeding in 220 cases (19,8%), resulting related to: previous surgery/RT, position, breathing, lesion size/ appearance/ depth, fissures/bone contact, muscle thickness and radiologist’ years of experience.

Conclusion
Lung biopsy with 21-Gauge needle represents the optimal compromise between diagnostic results, and no need for on-site evaluation, and complications, being also adequate for molecular analysis. Low rate and severity of complications make this technique ideal for patients affected with lung tumor, often affected by comorbidities.