Introduction/Background Smooth muscle tumor of uncertain malignant potential (STUMP) is a rare subtype of mesenchymal tumor in the gynecologic tract, which affects approximately 0.01% of patients treated by myomectomy or hysterectomy. These neoplasms may represent a ’transition’ tumor between leiomyoma to leiomyosarcoma. We report on a case of a 46-year-old woman, with a diagnosis of STUMP tumor.

Methodology A 42-year-old woman was referred to our department for surgical removal of uterus because she was diagnosed with STUMP tumor in a previous myomectomy. The pathology report of myomectomy revealed smooth muscle tumor of uncertain malignant potential, with local atypia and positive expression of p16, p53 and the ki67% was 15–20%. The decision of Multidisciplinary team (MDT) was that she should undergo a total hysterectomy with bilateral salpingo-oophorectomy. Upper abdominal and chest Computed Tomography (CT) and a Magnetic Resonance Imaging (MRI) scan of the lower abdomen were performed to stage the disease and they reported no findings. The patient’s preoperative serum level of cancer biomarkers was normal. In our department, the patient underwent a robotic total hysterectomy with bilateral salpingo-oophorectomy.

Results Histopathologically, after thorough gross processing of the specimen revealed a smooth muscle tumor of the uterus with a diameter measuring > 2.5 cm was identified. Microscopy did not show mitotic activity and nuclear atypia. Immunohistochemistry revealed focally mild immunopositivity. The decision of multidisciplinary team was to follow the patient closely.

Conclusion Stump tumors are rare neoplasms, with generally unknown malignancy potential. It is very difficult to differentiate between benign leiomyoma and malignant sarcomas preoperatively. However, these tumors can have metastatic potential and require aggressive treatment.

Disclosures Disclosures All authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this case report.