‘Atypical’ Pancreatic Endoscopic Ultrasound-Guided Fine Needle Aspiration ‘Atypical’ Pancreatic Endoscopic Ultrasound-Guided Fine Needle Aspiration Cytology: A Study of Interobserver AgreementCytology: A Study of Interobserver Agreement

Objectives The Papanicolaou Society of Cytopathology’s terminology scheme for endoscopic ultrasound-guided fine needle aspiration cytology includes an ‘atypical’ interpretation category. We conducted a retrospective study to determine the frequency of its use within our institution and the interobserver agreement among pathologists with variable experience in interpretation. Methods Following IRB approval, diagnoses of endoscopic ultrasound-guided fine needle aspiration procedures over a 6-year period, imaging studies and follow-up biopsy/resection results were collated. Eight pathologists blindly reviewed 18 ‘atypical’, 5 ‘benign’ and 5 ‘malignant’ cases using standard reporting terms. The free-marginal kappa (Kfree) was calculated to determine interobserver agreement. The ‘atypical’ reporting rate for each pathologist was also calculated. Results Of 598 pancreatic endoscopic ultrasound-guided fine needle aspiration, 29 (4.89%) were reported as ‘atypical’; In blinded review, Kfree showed slight agreement with the ‘atypical’ category (0.07) and fair agreement with the ‘benign’ and ‘malignant’ categories (0.34 and 0.22, respectively). Combining ‘suspicious’ and ‘malignant’ diagnoses increased the Kfree to 0.50 (moderate agreement). The pathologists had an acceptable mean ‘atypical’ reporting rate of 5.92% (standard deviation: 5, range: 12.2-0.7%). Conclusions The inter-observer agreement level for ‘atypical’ cases was lowest of all groups. Tracking atypical rates may be useful to measure the quality of the endoscopic ultrasound-guided fine needle aspiration interpretation service and as a measure of quality assurance in routine practice. Received July 25th, 2017-Accepted September 05th, 2017