Management and Outcomes of Uterine Smooth Muscle Tumour of Uncertain Malignant Potential ( STUMP )

BACKGROUND: Uterine smooth muscle tumours of uncertain malignant potential (STUMP) is a mesenchymal tumour which does not fulfil the criteria for leiomyoma, benign histological subtypes, or leiomyosarcoma. The risk factors for recurrence and the rates of recurrence vary amongst different studies; as a result, there are currently no consensus guidelines for optimal management. METHODS: Patients diagnosed with STUMP that were treated in a tertiary medical centre in Hong Kong were included in the study. The clinical and histological features were analysed and reviewed. Any adjuvant treatment was documented. Follow-up information, results of imaging studies and outcomes were obtained. RESULTS: Thirty-four patients with a diagnosis of STUMP were identified between 2002 and 2020. Three patients presented with atypical presentations including genital prolapse, an ovarian tumour and a fibroid polyp. Thirteen patients (38.2%) were diagnosed after abdominal myomectomy, 19 (55.6%) after a hysterectomy and 2 (6.2%) after other surgical procedures. Ten patients (66.6%) had a hysterectomy after primary surgery. Our patients were followed up every 3-6 months for the first 5 years then yearly with a median follow-up period of 6.5 years. Three patients (12.5%) developed a recurrence, all were leiomyosarcoma. The mean time for recurrence was 7.6 years. Four patients (30.7%) did not have a hysterectomy following a myomectomy and remained free of recurrence. CONCLUSION: Clinical and pathological factors influencing the risk of recurrence remain uncertain. With the lack of significant data, prognostic information and recommendations on follow up, management of these patients and their outcomes need to be further pooled and elaborated. This retrospective observational study reports the clinical course of this disease at a tertiary referral centre in Hong Kong.