CASE 12733 Published on 30.09.2015

Uterine smooth muscle tumour of uncertain malignant potential: an entity difficult to diagnose


Genital (female) imaging

Case Type

Clinical Cases


Xiropotamou ON1, Tsili AC1, Vrekousis Th2, Evagelou Ch2, Maliakas V1, Argyropoulou MI1

(1) Department of Clinical Radiology
(2) Department of Obstetrics and Gynaecology
Medical School,
University of Ioannina,
45110, Ioannina, Greece.

48 years, female

Area of Interest Genital / Reproductive system female ; Imaging Technique MR, MR-Diffusion/Perfusion
Clinical History
A 48-year-old woman was referred for abnormal vaginal bleeding of one year duration. Transvaginal sonography showed a large, heterogeneous, hypoechoic uterine mass, involving mainly the myometrium. Serum tumoral markers were normal. Diagnostic dilatation and curettage was inconclusive, due to the presence of necrotic material. MRI of the pelvis followed.
Imaging Findings
MRI revealed the presence of a large, heterogeneous myometrial uterine mass, protruding into the endometrial cavity and measuring 86 x 68 x 72 mm in dimensions (Figure 1). The lesion was inhomogeneous, mainly hyperintense on T2WI (Figure 1b), with areas of high signal on T1WI (Figure 1a), the latter suggestive of the presence of haemorrhage. No restricted diffusion was seen on the diffusion-weighted images (Figures 1c, d). The mass showed heterogeneous enhancement after gadolinium administration (Figure 1e). Neither tumour extension into the cervix nor pelvic lymphadenopathy was revealed.
Histology following total abdominal hysterectomy revealed the presence of uterine smooth muscle tumour of uncertain malignant potential.
Smooth muscle tumours of the uterus are benign and malignant [1-4]. The main representative of the benign and malignant category is leiomyoma and leiomyosarcoma, respectively [1-4]. On the other hand, there is a peculiar category, described as smooth muscle tumours of uncertain malignant potential (STUMP), in which the degree of malignancy pathologically is between leiomyoma and leiomyosarcoma [6-11]. The term “STUMP” comprises a heterogeneous group of rare tumours. The histologic diagnosis is often challenging. Histologic criteria distinguishing these neoplasms from benign leiomyomas include coagulative cell necrosis, moderate to severe cytologic atypia and numerous mitotic figures (Stanford). Among these, the factor strongly associated with malignant behaviour seems to be coagulative cell necrosis, characterized by an abrupt transition between viable cells and necrotic areas [6-10].
The MRI characteristics for these tumours are non-specific, closely resembling those of leiomyomas and leiomyosarcomas. Tanaka et al in a retrospective study of 24 smooth muscle uterine tumours concluded that the presence of more than 50% high signal on T2WI, of small high-signal areas on T1WI (probably representing areas of haemorrhage) and heterogeneous contrast enhancement, with unenhanced pockets (most probably representing areas of necrosis) were considered as more suggestive of the diagnosis of SMTUMPs and leiomyosarcomas [6].
Diffusion-weighted imaging may have an important complementary role in the characterization of myometrial tumours [12-14]. Thomassin-Naggara et al in a retrospective study of 51 myometrial tumours reported an overall accuracy of 92.4% in their characterization, by combining T2-weighted, high b value and ADC features. More specifically, in tumours with an intermediate T2-weighted and high b1, 000 signal intensity, an ADC value lower than 1.23 was considered as predictive of malignancy [14].
STUMPs are usually clinically benign but, in some cases, recurrence may occur. The reported time of recurrence varies between 15 months to 9 years, but a few data are available in the literature. Recurrences behave in a low-grade malignant fashion, following a disease-free interval and with a prolonged survival, even when they recur as leiomyosarcomas. Sites of recurrence include the pelvis, abdomen, liver, lungs, lymph nodes, humerus, retroperitoneum and uterus, if hysterectomy is not performed [6-11].
No standard protocols for the management of patients with suspected STUMP exist. Surveillance of these patients should be close and long-term. Close multidisciplinary management is mandatory.
Differential Diagnosis List
Smooth muscle tumour of the uterus of uncertain malignant potential
Focal myometrial contraction
Final Diagnosis
Smooth muscle tumour of the uterus of uncertain malignant potential
Case information
DOI: 10.1594/EURORAD/CASE.12733
ISSN: 1563-4086