Imaging characteristics of uterine smooth muscle tumors of uncertain malignant potential: a case report and literature review

Abstract

Uterine smooth muscle tumors of uncertain malignant potential (STUMPs) are rare tumors of the uterine myometrium that are often misdiagnosed, owing to limited knowledge of their characteristics on ultrasonography (US) and magnetic resonance imaging (MRI). We report a woman in her mid-30s who was hospitalized because of a pelvic tumor. A 6-cm mass was found in her lower left abdomen. US and MRI revealed a well-demarcated mass in the left adnexal area, with both cystic and solid elements, visible blood flow within the septa, a strong signal across >50% of the volume on T2-weighted imaging (T2WI), and a strong signal on diffusion-weighted imaging (DWI). After hysterectomy and bilateral salpingectomy, immunohistochemical examination confirmed STUMP. A review of the literature revealed characteristic imaging features of STUMP. Ultrasonography reveals STUMP as a solitary, well-circumscribed lesion with isoechoic or mixed echogenicity, the absence of posterior shadowing, and variations in blood flow. STUMP is characterized by strong signal intensity on T2WI, small areas of strong signal on T1WI, and non-enhancing cystic areas on contrast-enhanced MRI scans. Early diagnosis is crucial for the management and treatment of STUMP, and here we have summarized the imaging features of the lesion, thereby providing a valuable diagnostic reference.

Keywords: Smooth muscle tumor of uncertain malignant potential (STUMP); case report; imaging characteristic; magnetic resonance imaging; ultrasonography; uterus.

Figure 1.

Ultrasonographic images. (a) A 7.3-cm × 4.2-cm × 5.8-cm cystic/solid mass was detected in the left adnexal area, and this had multiple irregular septa, some of which were solid and (b) Color Doppler flow imaging revealed strip-like blood flow signals within the septa. Pulsed-wave Doppler indicated a resistance index of 0.37.

Figure 2.

Magnetic resonance images. (a) A 7.6-cm × 5.2-cm mixed cystic/solid lesion was identified in the left adnexal area. The lesion exhibited mixed signals, which were generally iso- to slightly hyperintense on T1-weighted imaging (a), and hyperintense signals on T2-weighted imaging (T2WI), with over 50% of the area showing a strong T2WI signal (b) diffusion-weighted imaging indicated that the lesion was attached to the left uterine wall (c) and showed restricted diffusion (d).

Figure 3.

Histopathologic findings. (a) Epithelioid tumor cells arranged in trabeculae and sheets, with abundant eosinophilic cytoplasm, mild atypia, and occasional mitotic figures, but no tumor necrosis. Hematoxylin and eosin; ×200 and (b) the Ki-67 proliferation index was high, reaching 23% in active areas. EliVision immunohistochemical staining; ×200.