Case ReviewsClassification of High-Grade Epithelial Carcinomas of the Ovary: Diagnostic Accuracy, Reproducibility, and Use of Ancillary TestingNakonechny, Quentin B. MD; Gilks, C. Blake MDAuthor Information From the Department of Pathology and Laboratory Medicine, Vancouver General Hospital and University of British Columbia, Vancouver, British Columbia, Canada. Reprints: C. Blake Gilks, MD, Rm 1253, 1st floor JPPN, Department of Pathology and Laboratory Medicine, Vancouver General Hospital, 855 West 10th Ave, Vancouver BC, V5Z 1M9, Canada. E-mail: firstname.lastname@example.org. The authors have no funding or conflicts to declare. AJSP: Reviews & Reports: 7/8 2016 - Volume 21 - Issue 4 - p 175-180 doi: 10.1097/PCR.0000000000000150 Buy Metrics Abstract The histotypes of ovarian carcinoma (eg, high-grade serous carcinoma, endometrioid carcinoma, clear cell carcinoma, mucinous carcinoma) are distinct diseases, differing with respect to precursor lesions, molecular abnormalities, association with hereditary cancer syndromes, and response to treatment. Although histotype diagnosis is straightforward in differentiated tumors, in high-grade carcinomas, the characteristic architectural and cytological features of the different histotypes may be lost, resulting in significant challenges in accurate histotype assignment. We present a case of high-grade carcinoma of the ovary in a young woman. The differential diagnosis was broad, based on examination of the hematoxylin-eosin–stained slides, as it showed solid architecture throughout, without cytological features characteristic of any of the Müllerian cell types. Through use of immunostains, it was possible to correctly diagnose the tumor histotype, leading to appropriate treatment and assessment of risk of a hereditary cancer syndrome. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.