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Background Pancreatic ductal adenocarcinoma (PDAC) can present as solid masses with cystic components that may be mistaken for other pancreatic cystic neoplasms. This study aimed to clarify the imaging features of atypical PDAC by focusing on endoscopic ultrasound (EUS) findings.Methods We retrospectively analyzed 35 patients with histopathologically confirmed PDAC who underwent EUS and imaging examinations. Additional techniques, such as elastography and contrast-enhanced (CE) EUS, were used for certain lesions. Tumors were classified into three subtypes according to the established imaging criteria. Features observed with EUS were compared with those observed with CE computed tomography (CT), CE magnetic resonance imaging (MRI), and fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT.Results All masses appeared hypoechoic, hypovascular, and hard on EUS; however, they appeared hypoechoic or anechoic on CE-EUS. Intratumoral cysts appeared as eccentric, round, anechoic areas with posterior acoustic enhancement and usually lacked septations, mural nodules, and ductal communication. Extratumoral cysts were classified as pseudocysts or retention cysts. On CE-EUS, the cystic component was anechoic, and elastography revealed a relatively soft cyst wall ( IDDF2026-ABS-0522 Figure 1. Endoscopic ultrasound image of a typical pancreatic cancer with cystic change). Cases were categorized as type 1 (n=21), type 2 (n=6), or type 3 (n=8). High interobserver agreement was achieved for tumor subtype discrimination (κ=0.867) and fine structure assessment with EUS. Tumor subtyping accuracy rates were 91% for EUS, 56% for CE-CT, 57% for CE-MRI, and 67% for FDG-PET/CT.Conclusions EUS may provide greater diagnostic accuracy than that of other imaging methods for characterizing and subtyping PDAC with cystic lesions.Abstract IDDF2026-ABS-0522 Figure 1