Diagnostic Categories and Key Features for Pathological Diagnosis of Endoscopic Ultrasound-Guided Fine Needle Aspiration Biopsy Samples of Pancreatic Lesions: A Consensus Study

This study aimed to establish a reliable and reproducible categorized diagnostic classification system with identification of key features to achieve accurate pathological diagnosis of endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) samples of pancreatic lesions. METHODS: Twelve pathologists examined virtual whole-slide images of EUS-FNAB samples obtained from 80 patients according to proposed diagnostic categories and key features for diagnosis. Fleiss κ was used to assess the concordance. RESULTS: A hierarchical diagnostic system consisting of the following 6 diagnostic categories was proposed: inadequate, nonneoplasm, indeterminate, ductal carcinoma, nonductal neoplasm, and unclassified neoplasm. Adopting these categories, the average κ value of participants was 0.677 (substantial agreement). Among these categories, ductal carcinoma and nonductal neoplasm showed high κ values of 0.866 and 0.837, respectively, which indicated the almost perfect agreement. Key features identified for diagnosing ductal carcinoma were necrosis in low-power appearance; structural atypia/abnormalities recognized by irregular glandular contours, including cribriform and nonuniform shapes; cellular atypia, including enlarged nuclei, irregular nuclear contours, and foamy gland changes; and haphazard glandular arrangement and stromal desmoplasia. CONCLUSIONS: The proposed hierarchical diagnostic classification system was proved to be useful for achieving reliable and reproducible diagnosis of EUS-FNAB specimens of pancreatic lesions based on evaluated histological features.