Uterine smooth muscle tumours of uncertain malignant potential: single-centre experience and review of the literature

Introduction
Uterine smooth muscle tumours of uncertain malignant potential (STUMPs) are a rare histologically heterogeneous group of uterine smooth muscle tumours (SMTs). Their malignant potential and clinical differentiation between leiomyoma and leiomyosarcoma remain uncertain prior to surgical removal.

Aim of the study
To investigate the patients and tumour characteristics of patients with STUMPs and to propose algorithms for optimal diagnosis, treatment, and follow-up management.

Material and methods
This was a single-centre retrospective cohort study of all patients who underwent surgery for a preoperative diagnosis of uterine myoma at the University Hospital “Dr. Georgi Stranski”, Pleven, Bulgaria during a period of 33 months (from January 2013 until October 2015). Data were obtained from the medical history records. We performed descriptive analysis to characterise the patient population (e.g. demographics, age, contraceptive use, and complaints that led to the diagnosis) and the tumour characteristics. Last data were obtained prior May 2019.

Results
A total of 320 medical records were retrospectively evaluated. The preoperative diagnosis of myoma was confirmed in 279 of the cases (89.4%). In 27 (8.3%) cases the final histological result was completely different. In 14 (2.3%) a histological postoperative diagnosis of STUMP was identified. All 14 STUMP lesions were intramural with a median size of 7.5 cm (range 3.5 to 15 cm). The median age at diagnosis of STUMP was 45.4 years (range 36 to 52 years), and 92.9% (n = 13) of the patients were premenopausal. Ultrasound data of a rapidly growing myoma were a reason for diagnosis in only three patients (25%), whereas 92.9% of the patients (n = 13) presented with heavy menstrual bleeding with or without anaemia. After surgery, none of the patients with STUMP experienced a relapse of the disease within the median follow-up time of 48 months (R = 40-78).

Conclusions
STUMP tumours are rare tumours, predominantly diagnosed in premenopausal women. They define a group of patients with very good long-term prognosis. Therefore, longer follow-up is needed to allow for conclusions on recurrence rate and survival.