Background and aims Macroscopic on-site evaluation (MOSE) is a practical method for real-time assessment of tissue adequacy during endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB). We evaluated the diagnostic yield and safety of MOSE-guided EUS-FNB using a novel Franseen-tip needle for solid and predominantly solid lesions. Methods This retrospective international multicenter study included 95 consecutive adults who underwent EUS-FNB with MOSE between May 2024 and January 2025. Eligible lesions were solid or predominantly solid (solid component >=75% when cystic features were present). The primary endpoint was diagnostic yield against a predefined final reference diagnosis. Secondary outcomes included number of passes, diagnostic yield in pancreatic versus non-pancreatic lesions, and adverse events. Results Mean age was 65.2 +/- 12.0 years, and 53 patients (55.8%) were male. Pancreatic lesions accounted for 64/95 cases (67.4%), and non-pancreatic lesions for 31/95 cases (32.6%). A 22-gauge needle was used in 92 procedures (96.8%), a 25-gauge needle in 2 (2.1%), and both gauges were reported in 1 procedure (1.1%). MOSE was performed in all cases. The mean number of passes was 2.42 +/- 0.83: 18 procedures required 1 pass, 22 required 2 passes, 52 required 3 passes, and 3 required 4 passes. Final diagnoses comprised 72 malignant lesions (75.8%) and 23 benign lesions (24.2%). Overall, 89/95 samples were diagnostic (93.7%), whereas 6/95 (6.3%) were non-diagnostic/inconclusive. Diagnostic yield was similar in pancreatic and non-pancreatic lesions (60/64 [93.8%] vs 29/31 [93.5%]). No procedure-related adverse events were recorded. Conclusions MOSE-guided EUS-FNB using a novel Franseen-tip needle achieved high diagnostic yield with few needle passes and a favorable safety profile across pancreatic and extra-pancreatic lesions. These findings support MOSE as a feasible adequacy-assessment strategy when ROSE is unavailable, while highlighting the need for prospective studies with standardized molecular-testing and follow-up protocols.
