AbstractBackground. Magnetic resonance imaging (MRI) provides precise staging of endometrial carcinoma. However, we have sometimes experienced patients with microscopic extrauterine extension in whom MRI showed the disease as being limited to the uterus. We studied indirect MRI signs for microscopic extrauterine spread of endometrial carcinoma which outwardly seemed to be limited to within the uterus. Methods. MRI studies and the clinical records of 100 patients with surgically proven endometrial carcinoma were retrospectively reviewed. We evaluated: (1) MRI staging, (2) tumor growing at the orifices of the fallopian tube in the uterine fundus, (3) hydrosalpinx, and (4) ascites, in each MRI study. Results. Surgical specimens showed that 12 of the 100 patients had extrauterine spread, with 1 patient showing both ovarian extension and omental metastasis; there ovarian extension in 3, extension to the fallopian tubes in 3, omental metastasis in 1, and positive peritoneal cytology in 4. Tumor growing at the orifices of the fallopian tubes with deep myometrial invasion showed higher accuracy for predicting microscopic intrauterine spread (82.0%) although it was not significantly different from the accuracy of deep myometrial invasion anywhere within the uterus (75.0%). However, tumor growing at the orifices of the fallopian tubes in a patients with stage Ia disease showed a high negative predictive value (89.7%). Hydrosalpinx had the highest specificity (98.9%) and accuracy (88.0%); however, it did not seem to be practical because it was observed in only 2 patients. Ascites in postmenopausal patients showed higher specificity (93.5%), although it was not considered to be useful in the premenopausal patients. Conclusion. Tumor extension at the orifices of the fallopian tubes in patients with stage Ia disease, and ascites in postmenopausal patients on MRI seemed to be predictive factors for microscopic extrauterine spread.