[1196] MELF Pattern of Myoinvasion in Endometrioid Endometrial Adenocarcinoma Is Associated with Low-Grade Tumors, Deep Myometrial Invasion and a Low Proliferative Index

Janet I Malowany, Amir Parsoei, Marcus Q Bernardini, Anthony Fyles, Marjan Rouzbahman. Toronto General Hospital, Toronto, Canada; University of Toronto, Toronto, Canada

Background: Low-grade and early-stage endometrioid endometrial adenocarcinoma (EEC) usually has a favorable outcome. There is a subset of patients with a microcystic, elongated and fragmented (MELF)-pattern of invasion that has been implicated with increased lymphovascular invasion (LVI) and lymph node metastases. Changes in immunohistochemical markers within MELF areas suggest these areas are distinct from the original tumor. This study characterizes the frequency of MELF-type invasion, its relationship with depth of myometrial invasion, LVI, changes in estrogen receptor (ER) status, E-cadherin and Ki67 expression.
Design: 286 cases of pure EEC were retrieved between 2001- 2011. The histological slides and clinical records were reviewed to record FIGO grade, depth of invasion, pattern of myometrial invasion, LVI and clinical outcome. A representative slide was selected to determine the expression of ER, E-cadherin and Ki67 within the tumor and in the MELF areas. Fisher's exact tests and student t-tests were used for statistical analyses.
Results: MELF was identified in 47 of 286 (16%) cases including 11 with focal areas of MELF. Tumors with MELF pattern were more likely to be grade 1 (76% v 51%), contain LVI and show invasion into outer half of myometrium. In FIGO grade 1 tumors, the MELF group was still more likely to contain LVI (62% v 26%, p<0.001) and invade into outer half of myometrium (65% v 33%, p<0.001). Disease recurrence and mortality were not significantly higher in MELF group. There was no significant difference in expression of ER and E-cadherin in MELF areas with the rest of the tumor. The proliferative index Ki67 appeared to be lower in at least 50% of cases in the MELF areas.

Table 1

	LVI present	Outer half myometrial invasion
Total EEC (all grades)	29%	38%
MELF cases (all grades)	72%	74%
Grade 1 EECs	26%	33%
Grade 1 with MELF	62%	65%

LVI and myometrial invasion in all tumors (grade 1-3) versus grade 1 tumors


Conclusions: MELF pattern of myoinvasion in EEC is more common in low-grade tumors. Within grade 1 tumors MELF pattern of myoinvasion is associated with deep myometrial invasion and LVI. Expression of ER and E-cadherin within the main tumor and MELF areas was similar in the majority of cases. However MELF areas demonstrated a lower proliferative index. This finding although appears unexpected for areas of active invasion, has been demonstrated in other malignancies.
Category: Gynecologic & Obstetrics

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 172, Tuesday Morning