To investigate whether the microcystic, elongated and fragmented (MELF) pattern of myometrial invasion encountered in certain endometrioid endometrial carcinomas can be considered as a risk factor for lymph node metastasis.

A total of 351 cases of total abdominal hysterectomy and bilateral salpingo-oophorectomy with/without lymphadenectomy or lymph node sampling, performed for endometrioid endometrial adenocarcinoma, were included in this study. The existence of MELF invasion, vascular invasion, fibromyxoid stromal reaction and lymph node metastasis were recorded. Immunohistochemistry for endothelial and epithelial markers was performed on selected cases. MELF invasion was identified in 20 (10.81%) and 13 cases (13.13%) treated without and with lymphadenectomy, respectively. All these cases were either well or moderately differentiated carcinomas, stages IA-II (without considering lymph node status). Positive lymph nodes were detected in seven of 13 MELF-positive (53.84%) and six of 86 MELF-negative cases (6.97%) This observation was statistically significant. Of the seven MELF-positive tumours with lymph node metastasis, three cases exhibited intravascular tumour emboli while four showed a fibromyxoid stromal reaction.

MELF pattern invasion was found to be related statistically to lymph node metastasis. Nevertheless, further studies are needed in order to evaluate the clinical significance of this observation.