The association of the microcystic, elongated and fragmented (MELF) invasion pattern in endometrial carcinomas with deep myometrial invasion, lymphovascular space invasion and lymph node metastasis.

The purpose of this study was to investigate the frequency of microcystic, elongated and fragmented (MELF) pattern of invasion in endometrioid endometrial adenocarcinomas (EA) and its association with prognostic factors. Stained tissue sections from 121 cases of EA (total hysterectomy and pelvic, with or without para-aortic, lymphadenectomy specimens) were reviewed to identify cases showing MELF-type invasion. The prognostic factors of low tumour grade, deep myometrial invasion (MI), cervical stromal involvement, lymphovascular space invasion (LVSI), lymph node (LN) metastasis and advanced clinical stage were more frequently observed in MELF-positive cases (p < 0.05). Thus, MELF-positive cases had an increased frequency (28/121) of these prognostic factors, which has implications in routine clinical practice, as it signals the importance of recognising MELF pattern invasion. In univariate analysis, MELF positivity, deep MI, cervical stroma involvement and LVSI were significantly related to LN metastasis (p < 0.05). However, in multivariate analysis, only MELF pattern invasion and cervical stroma involvement were independent factors for LN metastasis. Nevertheless, further studies are needed to evaluate the clinical significance of MELF pattern of invasion in endometrial adenocarcinoma.