Adequacy evaluation of 22-gauge needle endoscopic ultrasound-guided tissue acquisition samples and glass slides preparation for successful comprehensive genomic profiling testing: A single institute experience

Objectives: This study aimed to evaluate the successful sequencing rate of Foundation One CDx (F1CDx) using small tissue samples obtained with a 22-gauge needle (22G) through endoscopic ultrasound-guided fine needle acquisition (EUS-TA) and to propose guidelines for tissue quantity evaluation criteria and proper slide preparation in clinical practice. Methods: Between June 2019 and April 2024, 119 samples of 22G EUS-TA collected for F1CDx testing at Himeji Red Cross Hospital were retrospectively reviewed. Tissue adequacy was only assessed based on tumor cell percentage (≥20%). The procedure stopped when white tissue fragments reached 20 mm during macroscopic on-site evaluation. The specimens were prepared using both ‘tissue preserving sectioning’ to retain tissue within formalin-fixed paraffin-embedded blocks and the ‘thin sectioning matched needle gauge and tissue length’ method with calculation to ensure minimal unstained slides for the 1 mm³ sample volume criterion. Tissue area from HE slides and sample volume were measured, and F1CDx reports were analyzed. Results: Of 119 samples, 108 (90.8%) were suitable for F1CDx. Excluding the cases not submitted for testing, in the 45 cases where F1CDx was done using 22G EUS-TA samples, eight (17.8%) had a sum of tissue area tissue of 25 mm² or greater in the HE-stained sample. However, all cases met the F1CDx 1 mm³ volume criterion by submitting > 30 unstained slides per sample. As a result, 43 of 45 cases (95.6%) were successfully analyzable. Conclusions: The 22G EUS-TA needle is an effective tool for providing the sufficient tissue volume required for F1CDx.