, CT(ASCP) N Context.-Little has been reported on changes in pancreatic pathology practice after implementation of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA).Objectives.-We assessed the impact of EUS-FNA on cytologic diagnosis replacing histologic diagnosis for pancreatic disease and determined whether it fulfills Christensen criteria of a disruptive innovation effect.Design.-Pattern of utilization during 20 years, diagnostic categories, and diagnostic accuracy of pancreatic cytology were compared before and after implementation of EUS-FNA. The disruptive effect of cytology relevant to biopsy was assessed by comparing the utilization trends and the accuracy of diagnosis over time.Results.-The mean annual volume (standard deviation) of cytologic specimens increased from 24 (11) to 231 (10) after implementation of EUS-FNA, and that of histologic specimens increased from 97 (42) to 377 (148). The average percentage of annual cases managed by following cytology alone was 19% (10) before versus 51% (8) after implementation. The percentage managed by histology alone was 56% before versus 23% after implementation. Non-endoscopic ultrasound-guided fine-needle aspiration cytology decreased from 36% to 1%. Needle biopsies decreased from 7% to 1%, and other biopsy types from 29% to 9%. Unsatisfactory (7% versus 1%), atypical (16% versus 4%), and suspicious (16% versus 3%) diagnoses were significantly reduced. The accuracy of cytologic diagnosis significantly improved: the sensitivity (confidence interval) and specificity (confidence interval) for cancer diagnosis were 55% (38%-70%) and 78% (58%-89%) before versus 88% (84%-91%) and 96% (93%-98%) after implementation, respectively.Conclusions.-Endoscopic ultrasound-guided fine-needle aspiration improved the accuracy of cytologic diagnosis, reduced the number of indeterminate diagnoses, and replaced the need for tissue biopsy. Given its cost and simplicity as compared with tissue biopsy, this trend represents a disruptive innovation effect.