To investigate the clinical outcomes and histopathological features of uterine smooth muscle tumors of uncertain malignant potential (STUMP).

The study analysed cases diagnosed with uterine STUMP in a tertiary center, between January 2003 and September 2018. We investigated the clinical, operative and histopatholologic data of the cases. Follow-up information and clinical outcomes were also examined.

28 cases with uterine STUMP were studied. The mean age of the patients was 44.5 ± 9.0 years and the median parity was 2 (0–6). The mean tumor diameter was 6.3 cm (range 2–27 cm) and most (78.6%) of the tumors were located intramurally. In 25% of the cases diagnosis was after myomectomy, while in the others diagnosis was after hysterectomy. Of the patients who wanted to preserve the uterus and their fertility and who did not therefore undergo a subsequent hysterectomy, one patient became pregnant without any complication. One case with a history of myomectomy, presented as STUMP. The median follow-up time was 45.4 months (range 5–180). Recurrence occured in one case (3.7%) 33 months after diagnosis. Distant metastasis occurred in the lungs and the pathology of the biopsy was liposarcoma, and the patient died of the disease 62 months after diagnosis.

Uterine STUMP is a rare condition, and diagnosis can be difficult, often with unusual combinations of findings. Prognosis for the patient is unclear and their is a risk of recurrence with the tumors. To reduce mortality, regular follow-up and a centralised approach are recommended.