The importance of differential diagnosis in the imaging of uterus leiomyomas

Clinical History

A 51-year-old woman presented with right iliac fossa, right renal angle and pelvic pain. Her past history was unremarkable, except for the presence of a 3-cm intramural uterus leiomyoma.

Imaging Findings

Transabdominal and transvaginal ultrasound was performed, which demonstrated a 14 x 12 x 12 cm irregular complex heterogeneous mass in the midline of the pelvis. The uterus could not be separated from the mass (Fig. 1, 2). The ovaries were clearly separated from the mass and appeared unremarkable. Moderate bilateral hydronephrosis was noted.

The patient subsequently underwent MRI examination, which confirmed the presence of a large well-defined heterogeneous mass arising from the uterus and distorting the endometrial cavity (Fig. 3, 4, 5). The mass demonstrated areas of high T1 signal in keeping with haemorrhage (Fig. 6). T2 signal was variable, with areas of low, intermediate and high signal compared to normal myometrium. In addition, pressure effect from the pelvic mass was causing proximal ureteric obstruction with moderate bilateral hydronephrosis (Fig. 7). There was no lymphadenopathy, ascites or evidence of metastases within the imaged abdomen and pelvis.

Discussion

BACKGROUND: Uterine sarcomas are very rare, accounting for 1.3% of uterine malignancies [1]. By contrast, uterine leiomyomas are the most common benign tumour of the uterus, seen in up to 75% of women [1].

CLINICAL PERSPECTIVE: It is well recognised that differentiating uterine sarcomas from leiomyomas can be very difficult. Classic leiomyomas are well defined with low T1 signal and very low T2 signal with contrast enhancement on MRI, however, the clinical challenge arises when trying to differentiate an atypical degenerating fibroid from a leiomyosarcoma [2]. Historically this has not been such an issue as the majority of patients were treated with radical hysterectomy irrespective of the imaging appearances, and a definitive histological analysis was available post-operatively. However, with mini-invasive surgery, fertility-sparing management and endovascular techniques arising, it is becoming more important to obtain the correct diagnosis with imaging to ensure appropriate treatment planning [3].

IMAGING PERSPECTIVE: Along with clinical factors, e.g. rapid growth and failure to respond to non-surgical treatment, the following MRI features increase the likelihood of a diagnosis of uterine sarcoma: endometrial cavity not seen or thickened endometrial cavity [3]; intermediate T2 and high b1000 signal [3]; heterogeneous contrast enhancement [3]; intra-tumoural haemorrhage [3]; lesion hyperintensity on T2 in more than 50% of the tumour mass [4]; poorly defined margins [4]; avascular pockets on post contrast imaging most probably representing areas of necrosis on histology [5]; T1 hyperintensity [5]; ADC <1.096 [1]. The presence of hydronephrosis is not a differentiating characteristic between leiomyomas and uterine sarcomas, instead it reflects the increased pelvic pressure and can be present in both conditions.

OUTCOME: Our case highlights several of the above features, i.e. the endometrial cavity was not seen separately from the mass, and was rather expanded by the mass; there was evidence of intra-tumoural haemorrhage; the lesion was heterogeneous; and had grown to a large size in a short period of time. Unfortunately in this case, malignancy was not suggested pre-operatively although confirmed both surgically and pathologically. Post-operative CT chest (Fig. 8) showed multiple cannonball metastases. The patient died 6 weeks following surgery.

TAKE HOME MESSAGE: This case raises the difficulty in the pre-operative differentiation between uterus leiomyomas and leiomyosarcomas, based on imaging findings. In our patient, chest CT would have been valuable in confirming the malignant nature of the uterine mass.

Differential Diagnosis List

Final Diagnosis

FIGO stage IVB uterus leiomyosarcoma.

URL:	https://www.eurorad.org/case/12523
DOI:	10.1594/EURORAD/CASE.12523
ISSN:	1563-4086