MELF invasion in endometrial cancer as a risk factor for lymph node metastasis.

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.

Pavlakis K ，Messini I ，Vrekoussis T ，Panoskaltsis T ，Chrysanthakis D ，Yiannou P ，Voulgaris Z ... -  《-》

Lymphovascular space invasion in microcystic elongated and fragmented (MELF)-pattern well-differentiated endometrioid adenocarcinoma is associated with a higher rate of lymph node metastasis.

Hertel JD ，Huettner PC ，Pfeifer JD 《-》

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.

Dogan Altunpulluk M ，Kir G ，Topal CS ，Cetiner H ，Gocmen A ... -  《-》

Unusual epithelial and stromal changes in myoinvasive endometrioid adenocarcinoma: a study of their frequency, associated diagnostic problems, and prognostic significance.

Murray SK ，Young RH ，Scully RE 《INTERNATIONAL JOURNAL OF GYNECOLOGICAL PATHOLOGY》

Microcystic, elongated, and fragmented pattern invasion is mainly associated with isolated tumor cell pattern metastases in International Federation of Gynecology and Obstetrics grade I endometrioid endometrial cancer.

Although many studies have evaluated the impact of mismatch repair protein loss of expression (MMR LOE) or microcystic, elongated, and fragmented (MELF) pattern of myometrial invasion as individual factors in endometrial cancer, we analyzed the combined impact of both. We reviewed every case of International Federation of Gynecology and Obstetrics (FIGO) grade 1 endometrioid endometrial cancers (EECs) from our institution, between 2011 and 2015, that had a sentinel lymph node biopsy and/or a lymphadenectomy, and examined the following data: age, myometrial infiltration, MELF infiltration, lymphovascular space invasion, and lymph node status. These cases were then grouped according to the absence of lymph node metastases, the presence of isolated tumor cell (ITC) lymph node metastases, or the presence of non-ITC metastases. Among the 127 cases that were in our study, 105 patients did not have nodal metastases, whereas 22 patients showed metastases, of which 11 were ITC. MMR LOE was only significantly associated with a higher odds ratio (OR) of metastases (OR, 7.44; P < .001). MELF was only associated with a higher OR of ITC-pattern metastases (OR, 32.3; P < .001). This study distinguished the effects of MELF and MMR LOE on the risk of metastases in FIGO grade 1 EEC. Further research on the clinical impact of MELF and ITC-pattern metastases is warranted to better guide clinicians on the management of patients with FIGO grade 1 EEC harboring such characteristics, which are still considered low-risk cancer.

Pelletier MP ，Trinh VQ ，Stephenson P ，Mes-Masson AM ，Samouelian V ，Provencher DM ，Rahimi K ... -  《-》