Association of Local and Distant Organ Metastases With MELF Pattern in Endometrial Cancer.

Several types of myometrial invasion in endometrioid-type endometrial adenocarcinoma (EEC) have been identified: adenomyosis-like changes; adenoma malignum; broad front, single-cell/cell clusters; and the microcystic elongated and fragmented (MELF) pattern. This study aims to investigate the effect of the MELF pattern on recurrence type and survival rate among patients with EEC. We retrospectively reviewed the records of patients diagnosed with EEC over a 10-year period from January 2011 to January 2021. Among 108 patients with EEC, 54 had recurrence (study group), and 54 did not (control group). The MELF pattern was more common in the group with recurrence than in the group without recurrence (40.7% vs. 14.8%; P=0.002). The MELF pattern was observed in 60.0% of patients with local recurrence and 29.4% of patients with extrapelvic or distant organ metastases (P=0.027). Evaluation of 5-year disease-free survival (P=0.003) and overall survival (P=0.001) rates showed that MELF positivity was associated with decreased survival. Among patients with grade I-II EEC lacking uterine-localized myometrial invasion, the MELF pattern was less common in the nonrelapsed group than in the local relapse group (10.0% vs. 60.0%; P<0.001). The MELF pattern (odds ratio=19.4, 95% CI=1.2-31.2) was a significant independent negative predictor for local recurrence. The MELF pattern was more common in patients with recurrence, especially local recurrence. This finding suggests that the MELF pattern primarily impacts direct local invasion rather than hematogenous or lymphatic spread.