Smooth muscle tumour of uncertain malignant potential (STUMP) diagnosed by hysteroscopic surgery : Report of a case

Smooth muscle tumour of uncertain malignant potential (STUMP) is a rare neoplasia which is a variant of smooth muscle tumor. We report a case of "STUMP" occurring in a 44-year-old female. She was referred to our hospital with complaint of hypermenorrhea and dysmenorrhea. Magnetic resonance imaging (MRI) showed tumors about 6cm in diameter at the myometrium, and about 5cm in diameter at the uterine cavity which were suspected to be uterine myomas. She underwent a hysteroscopic resection for submucosal tumor. The resected tumor grew in interlacing bundles of smooth muscle cells displaying moderate cytologic atypia and a mitotic index of three to four mitotic figures per 10 high power fields (HPFs). Coagulative tumor cell necrosis or hemorrhage were not seen. The tumor cell showed positive staining for α-SMA, while staining for both CD10 and HMB45 was negative. Ki-67 was positive in occasional neoplastic cells. The final diagnosis was "STUMP", and she had a total abdominal hysterectomy.  Although uterine leiomyoma is the most common benign neoplasm of the female genital tract, resected specimens should be submitted for pathological examination. Patients diagnosed with "STUMP" should receive long-term surveillance because of its "uncertain potential".