Original ArticlesThe Microcystic, Elongated, and Fragmented (MELF) Pattern of Invasion A Single Institution Report of 464 Consecutive FIGO Grade 1 Endometrial Endometrioid AdenocarcinomasJoehlin-Price, Amy S. MD*; McHugh, Kelsey E. MD*; Stephens, Julie A. MS†; Li, Zaibo MD, PhD*; Backes, Floor J. MD‡; Cohn, David E. MD‡; Cohen, David W. MD*; Suarez, Adrian A. MD*Author Information *Department of Pathology †Center for Biostatistics ‡Department of Obstetrics and Gynecology, The Ohio State University Wexner Medical Center, Columbus, OH Conflicts of Interest and Source of Funding: J.A.S. was supported by Award Number Grant UL1TR001070 from the National Center For Advancing Translational Sciences. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Adrian A. Suarez, MD, Department of Pathology, The Ohio State University Wexner Medical Center, 410 W 10th Avenue, Columbus, OH 43210 (e-mail: [email protected]). The American Journal of Surgical Pathology: January 2017 - Volume 41 - Issue 1 - p 49-55 doi: 10.1097/PAS.0000000000000754 Buy Metrics Abstract MELF invasion has been associated with nonvaginal recurrences and lymph node (LN) metastases in multi-institutional case control studies but has not been well examined in large single-institution cohorts. Hysterectomy specimens with FIGO 1 endometrioid endometrial carcinoma and lymphadenectomies from 2007 to 2012 were identified. Electronic medical records and histologic slides were reviewed. Of 464 identified cases, 163 (35.1%) were noninvasive, 60 (12.9%) had MELF, 222 (47.8%) had a component of the infiltrative invasion pattern without MELF, 13 (2.8%) had pure pushing borders of invasion, 5 (1.1%) had pure adenomyosis-like invasion, and 1 (0.2%) had pure adenoma malignum-like invasion. Sixteen cases had LN metastases. Significantly more MELF cases had positive LNs than non-MELF cases overall (18.3% vs. 1.2%, P<0.001). The results were almost identical when invasive infiltrative cases with and without MELF were compared (18.3% vs. 1.8%, P<0.001). The maximum number of MELF glands per slide did not differ between cases with and without LN metastases, P=0.137. A majority of positive LNs, even in MELF cases, demonstrated nonhistiocyte-like metastases. Only 5 cases (all with MELF invasion) demonstrated micrometastatic lesions or isolated tumor cells only. MELF cases demonstrated a nonsignificant decrease in time to extravaginal recurrence (P=0.082, log-rank test), for which analysis was limited by low recurrence rates. In summary, MELF is associated with LN metastases, even when compared with other infiltrative cases and shows multiple patterns of growth in positive LNs. MELF cases additionally trended toward decreased time to extravaginal recurrence. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.