Background: Early-stage low-grade endometrial carcinoma has an excellent prognosis. In few cases local relapse and/or distant metastases can occur. We report the muscle as an unusual site of metastasis. Case: A 69-year-old woman underwent surgery for FIGO Stage IA, grade 1 endometrioid adenocarcinoma of the endometrium. After four years she had local relapse without response to chemoradiation, requiring pelvic exanteration. Three years later she was diagnosed with a deltoid muscle metastasis confirmed histologically and bone metastases. After failing hormone therapy, chemotherapy was administered. She died eight months after diagnosis of the bone and muscle metastases. Conclusion: Low-risk endometrial carcinoma can behave like a high-risk group. Furthermore, this report describes, to our knowledge, the first case of endometrial carcinoma muscle metastasis.