[1086] Interobserver Variability in the Interpretation of Tumor Cell Necrosis (TCN) in Uterine Leiomyosarcoma (LMS).

Diana Lim, Blake Gilks, Teri Longacre, Marisa R Nucci, Robert A Soslow, Esther Oliva. National University Health System, Singapore, Singapore; Vancouver General Hospital, BC, Canada; Stanford University, CA; Brigham and Women's Hospital, Boston, MA; Memorial Sloan Kettering Cancer Center, New York, NY; Massachusetts General Hospital, Boston

Background: Distinction of LMS from leiomyoma is based on: 1) nuclear atypia, 2) mitotic rate and 3) TCN. Unlike ischemic-type necrosis which may be seen in benign and malignant smooth muscle tumors (SMTs), TCN is thought to be unique to LMS. The distinction between these two types of necrosis can be challenging, especially during early stages, when necrotic foci are limited or when they exhibit overlapping features. The aim of this study was to assess the interobserver variability in the interpretation of TCN in uterine LMS.
Design: 34 LMS were retrieved and a representative H&E slide showing one or more areas of necrosis was selected from each case. Pathologists from 6 different institutions subspecializing in gynecologic pathology performed a blinded, independent review of the slides. Using the current WHO criteria for assessment of TCN, they had to classify the necrotic foci into: 1) TCN, 2) no TCN or 3) indeterminate for TCN. Agreement among the panelists was categorized as: full agreement—all pathologists in agreement; partial agreement—4 or 5 pathologists in agreement; no agreement—≤ 3 pathologists placing the case into the same category.
Results: Full agreement regarding the presence or absence of TCN was reached in 12 cases (35%) (7 thought to show TCN); partial agreement in 16 (47%); and no general consensus in 6 cases (18%). Overall, the level of agreement was fair (k=0.3948). In 8 of the 34 cases (23.5%), ≥ 1 pathologist made a diagnosis of "TCN" and ≥ 1 pathologist made the diagnosis of "no TCN" in the same case. The number of cases diagnosed as “indeterminate for TCN” by each pathologist ranged from 0 to 10 with a mean of 5.8. In 20 cases, at least 1 pathologist diagnosed “indeterminate for TCN” (59%); at least 2 were undecided in 10 (29%), and at least 3 in 4 cases (12%). Four pathologists diagnosed “indeterminate for TCN” in 1 case.
Conclusions: The level of interobserver agreement amongst experienced gynecological pathologists in the assessment of TCN in uterine LMS is only fair. These results further reiterate the importance of assessing for both nuclear atypia and mitotic activity when differentiating between benign and malignant SMTs and not relying solely on the presence of TCN.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 8:00 AM

Platform Session: Section D, Tuesday Morning


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