The majority of cases with endometrial cancer (EC) have low grade endometrioid type disease which has a favorable prognosis. However, a subgroup of these patients shows a more aggressive clinical course. There are several risk factors defined for the aggressive course including tumor diameter, cervical involvement, depth of myometrial invasion, and lymphovascular space invasion. The morphologic pattern of myometrial invasion was also suggested to be one of the risk factors associated with unfavorable prognosis in these patients. A retrospective study was conducted to investigate the role of microcystic elongated and fragmented (MELF) pattern of myometrial invasion (MI) in patients with low grade endometrioid type EC. Of 276 cases, 69 (25.0%) had MELF pattern of MI. The rate of lymph node metastasis was higher in patients with MELF pattern of MI which was an independent risk factor for lymphatic dissemination (p< 0.001). Also, MELF pattern of MI was significantly associated with decreased disease-free survival (DFS) (p= 0.015). In conclusion, in patients with low grade endometrioid type EC, the presence of MELF pattern of MI is associated with the more aggressive clinical course since it is associated with higher rate of lymphatic metastasis and decreased disease-free survival.