Uterine Smooth Muscle Tumors of Uncertain Malignant Potential (STUMP): Clinical Course and Follow-Up Outcomes After Surgery.

BACKGROUND

Uterine smooth muscle tumor of uncertain malignant potential (STUMP) is a rare "gray-zone" entity characterized by unpredictable postoperative behavior and the absence of standardized surveillance strategies.

OBJECTIVE

To describe postoperative clinical course, recurrence patterns, and fertility-related outcomes in patients with STUMP managed at a tertiary center.

METHODS

We conducted a retrospective observational study including 27 patients with a final pathology diagnosis of STUMP who underwent surgery and had postoperative follow-up available between 2009 and 2025. Clinical, surgical, and pathological variables were collected from hospital records. Recurrence was defined as radiologic evidence of a new lesion during follow-up and categorized by anatomic site. Outcomes included recurrence status, time to recurrence, recurrence histology, subsequent management, and pregnancy outcomes after uterus-sparing surgery.

RESULTS

Median follow-up was 58 months (IQR 17-79; range 4-136). Recurrence occurred in six patients (22.2%), with a median time to recurrence of 36 months (IQR 8-66.3). Recurrences were local (n = 4) or pulmonary (n = 2); one patient with lung recurrence also had wrist soft-tissue involvement. Histology at recurrence included leiomyosarcoma (n = 2), STUMP (n = 2), and leiomyoma (n = 2). All recurrent cases underwent secondary surgery. One death occurred during follow-up. Uterus-sparing surgery was performed in nine patients (33.3%); recurrence occurred in four, all local. Two pregnancies were recorded, including one live birth.

CONCLUSION

STUMP shows heterogeneous postoperative behavior, including late and occasionally malignant or distant recurrences. Long-term surveillance is warranted, and uterus-sparing management may be considered in carefully selected patients with fertility goals under close follow-up.