CONTEXT: The WHO Classification of Tumors of the Digestive System (2019) categorizes WDPanNETs as grade 1 (G1), grade 2 (G2) or grade 3 (G3) by mitotic count and proliferative index (KI67). We examined the performance of pathologists and pathology trainees in grading WDPanNET according to the 2019 WHO Classification.
DESIGN: One H&E and KI-67 slides of eleven WDPanNET cases from our 2023 archives (7 G1, 1 G2 and 3 G3) were blindly evaluated by 2 junior residents (PGY-1), 2 senior residents (PGY-3), 2 pathologists without formal gastrointestinal training (NOGIP) and 2 pathologists with formal gastrointestinal training (GIP), provided with the 2019 WHO Classification. Their grading was compared with the reported grade of the case. Interrater agreement, accuracy and concordance by level of training were calculated.
RESULTS: The group interrater reliability was weak to moderate (ĸ = 0.488; z = 0.0189; p-value 0.985). Overall accuracy was 72.7%. By level of training, accuracy and (concordance) were 72.73% (81.82%) GIP, 81.82% (63.64%) NOGIP, 77.27% (72.73%) PGY-3 and 59.1% (54.55%) PGY-1. Only 2 cases (G1) were correctly classified by all participants. Grade accuracy was G3 (79.16%), G1 (71.42 %) and G2 (62.5%). Grade concordance was lowest (33.33%) for G3 by NOGIP followed by 42.86% for G1 by PGY-1. For G2 and G3, KI-67 was the determinant factor in all but one event. Eyeballing was the predominant method for KI-67 scoring.
CONCLUSIONS: Agreement was weak or at best moderate irrespective of level of training. There was remarkable variability in the KI-67 score among participants.