To explore the diagnostic characteristics of uterine submucosal adenomyoma (SA).

We retrospectively analyzed the clinical, imaging, laboratory, and pathological data of a single patient with SA, who was admitted to the Department of Gynecology, South China Hospital Affiliated to Shenzhen University on February 13, 2025. The diagnostic characteristics of SA were summarized.

This patient was a 29-year-old female with abnormal menstrual bleeding since 2022, without any obvious cause. Menstrual cycles were regular, but flow varied from spotting to episodes over threefold her usual volume, with clots. She didn′t have significant dizziness, fatigue, fever, headache, blurred vision or other discomforts. The ultrasound (US) showed progressive endometrial thickening: 38 mm in 2022, increasing to 68 mm.The endometrium was heterogeneously hyperechoic with multiple irregular cystic components. The enhanced MRI showed abnormal signals in the uterine cavity, suggesting a benign lesion; endometrial hyperplasia with hemorrhage and necrosis was considered. The carbohydrate antigen 125 level mildly elevated (39.8 U/mL), and the human epididymis protein 4 level significantly elevated (98.4 pmol/L). In 2024, histopathology of 2 hysteroscopic biopsies both suggested the possibility of endometrial hyperplasia. In February 2025, the third hysteroscopic resection of uterine lesions and percutaneous uterine biopsy under US guidance suggested the possibility of SA lesion.

Suspicion for SA should be raised in cases of abnormal menstruation flow with progressive endometrial thickening and cystic components. Combining MRI assessment with targeted biopsy can improve preoperative diagnostic accuracy.