Minimal deviation endometrioid adenocarcinoma (MDA-E) of the endometrium is a rare pathological entity, and its radiological features are rarely documented. A 73-year-old Japanese woman was referred to the authors when an endometrial biopsy revealed moderately differentiated endometrioid adenocarcinoma. Preoperative radiological examinations, including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) showed no evidence of cancer nests. In the hysterectomy specimen, mildly atypical glands were scattered throughout the entire depth of the myometrium, without stromal desmoplastic reaction, and a tiny focus of typical, ruptured, endometrioid adenocarcinoma glands was found in the atrophic endometrium. MRI had not been able to identify this unusual, scattered, myometrial invasion. It should be kept in mind that in cases showing Stage IA endometrial carcinoma without endometrial thickening on MRI, this rare form of invasion may be present.