Endocrine Pathology

511 Assessing Resident Frozen Section Diagnostic Skills for Endometrial Cancer William Selove, Thomas Stockl, Dina Kandil, Leslie Bradford, Yuxin Liu. University of Massachusetts Medical School, Worcester, MA; UMass Memorial Hospital, Worcester, MA. Background: The development of frozen section diagnostic skills is a critical part of pathology residency training. Our study aims to assess trainee performance on endometrial cancer frozen sections and to identify common errors while providing recommendations for improvement. Design: Twenty-two residents at our institute (ranging from PGY1 to PGY5) performed a total of 260 endometrial cancer frozen sections from 2011 to 2014. Their independent frozen section diagnoses, including tumor type, grade, and myometrial invasion, were compared with the final pathology reports. Results: Endometrial cancer type and grade were accurately diagnosed by residents on frozen sections in 194 of 260 cases (75%). The misdiagnosed cases resulted from undercalling endometrioid tumor grade in 43 cases (17%), overcalling in 6 (2%), and missing Type II tumor component in 17 (6%), including 7 serous carcinoma, 5 clear cell carcinoma, and 5 carcinosarcoma. (Shown in figure 1, A/B clear cell carcinoma; C/D Serous carcinoma both misdiagnosed as Grade 1 Endometrioid carcinoma on frozen section.)