1. To compare diagnostic accuracy between EUS-guided and US-guided biopsy approaches in pancreatis solid tumors. 2. To evaluate procedural safety, including complication rates such as bleeding and pancreatitis. 3. To assess sample adequacy, number of passes required, technical success rates and cost-effectiveness of the two methods.

A retrospective analysis was conducted at Military Medical Academy – Sofia, including 170 consecutive patients with suspected pancreatic solid tumors who underwent pancreatic biopsy between January 2024 and December 2024. Patients were divided into two groups – the first with patients who underwent endoscopic ultrasound guided (EUS-guided) pancreatic biopsy and the second with patients who underwent ultrasound guided (US-guided) pancreatic biopsy. For the patients in the EUS group 22G needle was used and for the patients in the US group 18G needle was used.

After the final analysis, we found that the male-to-female ratio in the two groups was equivalent: 50.5% to 49.5%. The mean age in the US-guided core biopsy group was 66.5 years, and the mean age in the EUS-guided biopsy group was 70 years. The mean size of the pancreatic solid tumor in the US group was 38.75 mm, and the mean size of the solid pancreatic lesions in the EUS group was 34.65 mm. The mean number of needle passes in both groups was two. ERCP was performed in 50.5% of the patients in the US group and in 44.1% of those in the EUS group. The mean hospital stay was 4 days in the US group and 4.6 days in the EUS group. The most common complications were pancreatitis and bleeding. We found that ERCP was an independent risk factor for complications. The rate of pancreatitis in the US group was 1.17% without ERCP and 8.23% with ERCP in addition to the biopsy. The rate of bleeding in the US group was 1.17% without ERCP and 10.58% with ERCP. In the EUS group, the rate of pancreatitis was 2.35% without ERCP and 11.62% with ERCP. Bleeding occurred in 3.52% of the patients undergoing EUS-guided biopsy without ERCP and in 8.23% of those with ERCP. Histology results in the US group showed 86% pancreatic adenocarcinoma, 11% chronic pancreatitis, and 3% other solid pancreatic lesions. In the EUS group, pancreatic adenocarcinoma was diagnosed in 77% of the patients, chronic pancreatitis in 10%, and other solid lesions in 13%.The positive predictive value in the US group was 100%, the negative predictive value was 90.12%, sensitivity was 100%, specificity was 99%, and overall accuracy was 98.70%. In the EUS group, the positive predictive value was 98.48%, the negative predictive value was 47.48%, sensitivity was 91%, specificity was 86.70%, and overall accuracy was 87.20%.

US-guided core biopsy demonstrated higher diagnostic accuracy (98.70%) compared to EUS-guided biopsy (87.20%) in this cohort of 170 patients. Although both techniques required a similar number of passes and had comparable safety profiles, ERCP significantly increased the risk of pancreatitis and bleeding in both groups. EUS was more frequently associated with pancreatitis, while US-guided biopsy showed higher bleeding rates when combined with ERCP.