Background: Endometrial adenocarcinoma is very uncommon in women under 40 years of age. Case: A 39-year-old woman with tuberous sclerosis and severe intellectual disability presented with irregular bleeding unresponsive to oral contraceptive therapy. She was subsequently found to have a deeply invasive endometrial adenocarcinoma. Conclusion: Caregivers must pay particular attention to signs and symptoms in non-verbal patients. Persistent irregular bleeding on oral contraceptive therapy warrants additional evaluation.