Is microcystic, elongated, and fragmented pattern of myometrial invasion in endometrioid endometrial carcinoma associated with survival?

BACKGROUND: Microcystic, elongated, and fragmented (MELF) pattern is one of the myometrial invasion patterns in endometrioid endometrial carcinoma (EEC), and it has been associated with poor prognostic parameters, especially lymphovascular space invasion (LVSI) and lymph node metastasis (LNM). This study aims to represent the frequency of MELF pattern in EEC and the relationship between MELF pattern with clinicopathological parameters, overall survival (OS), and disease-free survival (DFS).

METHODS: In this retrospective cohort study, we examined 233 patients with EEC diagnoses with the result of a total hysterectomy and bilateral salpingo-oophorectomy between 2009 and 2014. The association of MELF pattern with risk factors such as stage, recurrence, and survival was analysed statistically with the comparison of MELF positive and negative cases.

RESULTS: MELF pattern was seen in 21.8% of all cases (51/233) and 23% of grade 1-2 cases (50/217). The MELF pattern showed a significant difference among patients when they were compared according to advanced age (≥60) (p = 0.022), LVSI (p = 0.021), deep myometrial invasion (p < 0.01), LNM (p = 0.027), and advanced FIGO stage (p = 0.043). MELF pattern was a predictive factor of LNM in univariate logistic regression analysis but did not show significance in multivariate analysis. The Kaplan-Meier survival analysis showed that MELF positive cases had reduced OS (66.7% vs 79.7% p = 0.003) and DFS (66.7% vs 77.5% p = 0.017) rates. In the univariate analyses, MELF pattern was an independent prognostic factor on OS and DFS along with other parameters, while it was not observed to maintain this effect in the multivariate analyses.

DISCUSSION: This study is one of the largest series examining the relationship between MELF pattern of myometrial invasion and survival, and our results represented that the MELF pattern is associated with the worse clinical outcome since it is associated with lymphovascular space invasion, deep myometrial invasion, lymph node metastasis, and reduced overall survival and disease-free survival rates. Although the presence of MELF pattern is not reported in routine practice, it may be used as an indicator that will help predict a worse outcome.