Abstract
RATIONALE: Intramural adenosarcoma of the uterine myometrium is an uncommon gynecologic malignancy, often diagnosed postoperatively, and may arise from pre-existing benign lesions such as adenomyoma. PATIENT CONCERNS: A 46-year-old woman presented with irregular vaginal bleeding during the postmenstrual period for 3 months. She had a prior history of adenomyoma resection and breast cancer treated with tamoxifen. DIAGNOSES: Pelvic ultrasonography suggested multiple uterine myomas. Histopathological and immunohistochemical analyses of the resected specimen confirmed low-grade malignant uterine adenosarcoma originating from adenomyoma. INTERVENTIONS: The patient underwent a lower abdominal hysterectomy with bilateral adnexectomy. OUTCOMES: Postoperative recovery was uneventful. No adjuvant therapy was administered, and the patient remains under regular oncology follow-up without recurrence to date. LESSONS: This case highlights the potential for malignant transformation of adenomyoma into intramural adenosarcoma and underscores the importance of thorough histopathological evaluation in patients with recurrent or atypical uterine masses.