Clinicopathological and prognostic significance of the microcystic elongated and fragmented pattern in endometrial cancer: a systematic review and meta-analysis.

Objective: The presence of the microcystic elongated and fragmented (MELF) pattern, distinguished by its microcystic, elongated and fragmented attributes, constitutes a common manifestation of myometrial invasion (MI) within endometrial carcinoma. However, the prognostic significance of this pattern has not been definitively established. Consequently, this research aimed to clarify the prognostic implications of the MELF pattern for individuals diagnosed with endometrial carcinoma.

Design: Systematic review and meta-analysis of observational clinical studies.

Data sources: An extensive review of the literature was conducted using reputable databases such as PubMed, Embase, Web of Science and the Cochrane Library, covering the period from January 2003 to October 2023. Search terms encompassed endometrial cancer and the MELF pattern.

Eligibility criteria for selecting studies: The inclusion criteria were patients who had undergone hysterectomy and whose pathology confirmed endometrial endometrioid carcinoma, with or without MELF infiltration.

Data extraction and synthesis: Two reviewers performed data extraction separately. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). Stata V.17.0 software was used for statistical analysis.

Results: The meta-analysis incorporated 16 retrospective cohort studies. Employing a fixed-effects approach, the analysis demonstrated an association of the MELF pattern with reduced overall survival (HR 2.21, 95% CI 1.50-3.25, p=0.000) and lower disease-free survival rates among patients with endometrial cancer (HR 1.72, 95% CI 1.17 to 2.55, p=0.006). Furthermore, aggregated data revealed a linkage between the MELF pattern and significant MI, nodal metastasis, involvement of the lymphovascular space, penetration of the cervical stroma and progression to advanced stages of endometrial carcinoma.

Conclusion: The MELF pattern serves as a significant adverse prognostic factor in endometrial cancer, warranting increased attention.