MELF pattern of myometrial invasion and role in possible endometrial cancer diagnostic pathway: A systematic review of the literature

Microcystic, elongated, fragmented (MELF) pattern of myometrial invasion has been proposed as a prognostic marker in patients with endometrial carcinoma (EC). Its prognostic and predictive effect still remains elusive. The aim of the present study is to accumulate the current knowledge on the role of MELF pattern in the prognosis and survival of patients with EC. Medline, Scopus, Google Scholar, and Clinicaltrials.gov databases were searched for articles published up to May 2018, along with the references of all articles. Prospective and retrospective trials reporting outcomes of cases with EC who were examined for MELF pattern were considered eligible for inclusion in the present systematic review. Of the 196 records screened, 14 were considered eligible. A total of 14 studies which comprised 588 women were finally included in the present systematic review. All the included patients were evaluated for presence of MELF pattern of myometrial invasion. MELF positive (+) patients were more likely to present with larger and higher grade tumors, lymph node metastasis, lymphovascular invasion and >50% myometrial invasion. No difference was reported in disease free survival (DFS) and disease specific survival (DSS) as well as in vaginal recurrence rates. MELF (+) was reported as a significant indicator of survival. In conclusion, MELF pattern of myometrial invasion plays a critical role in lymphovascular space invasion and lymph node metastasis in patients with EC. Regardless, its implication in survival and recurrences is ill determined.