Uterine Rhabdomyosarcoma.

Clinical History

A 65-year-old woman presented with a 2-month history of postmenopausal bleeding. Pelvic examination revealed a large ulcerated mass filling the upper vagina. Routine blood tests demonstrated mild microcytic anemia.

Imaging Findings

CT imaging showed a large mass in the lower uterus and cervix (Fig.1a-b). There was no disease outside the pelvis.

On MRI, the mass was shown to arise from the uterus protruding into the cervix and upper vagina which were expanded by the tumour but not invaded (Fig.2-3). The mass measured 6.5x6.8x6.6 cm and was hypo intense on T1-weighted sequences (Fig.4) and heterogeneously hyper intense on T2-weighted images (Fig.2-3). Superiorly there was a low T2-weighted signal fibrovascular stalk which arose from the posterior myometrium that enhanced on post-gadolinium sequences (Fig.2 and 5. The mass also demonstrated restricted diffusion (Fig.6). There was no extra-uterine tumour extension or lymph node involvement.

The patient underwent total hysterectomy and bilateral salpingo-oophorectomy. Histology reported a rhabdomyosarcoma. Postoperatively, the patient had chemotherapy and radiotherapy. The patient remains well with no evidence of recurrent disease.

Discussion

Uterine sarcomas are uncommon mesenchymal tumours. The predominant types are leiomyosarcomas and endometrial stromal sarcomas. Pure rhabdomyosarcomas (RMS) are an exceptionally rare category of uterine sarcoma that show evidence of skeletal or striated muscle differentiation [1]. There are three major histological subgroups of RMS – embryonal, alveolar and pleomorphic. Pleomorphic RMS occur almost exclusively in adults whilst embryonal and alveolar arise primarily in children and adolescents [2]. Presenting symptoms include pelvic pain, abnormal vaginal bleeding, prolapsing tissue into the introitus and a palpable abdominal mass.
Pleomorphic and alveolar RMS are typically aggressive neoplasms often demonstrating extrauterine spread at diagnosis. Alternatively, embryonal RMS often present at an earlier stage and in turn have a better prognosis [3, 4]. Clinical distinction between RMS and other uterine malignancies is challenging and imaging plays a pivotal role. All variants of uterine RMS are usually large and polypoidal at presentation. The chief role of CT is assessing the presence of metastatic disease. Contrast enhanced CT usually shows a soft tissue lesion with variable enhancement. MRI is the modality of choice for tumour characterisation and for better anatomical localisation. On T1-weighted images lesions show moderately low signal with occasional intrinsic high signal haemorrhagic foci. On T2-weighted images lesions show heterogenous high signal intensity. Enhancement is inhomogenous following gadolinium administration, with pleomorphic and alveolar subtypes often exhibiting central poorly enhancing regions, which reflect intra-tumoural necrosis. Lesions usually demonstrate moderate restricted diffusion on DWI. Ultimately definitive diagnosis is made on histopathological examination of a biopsy specimen or of the resected tumour.

Treatment is usually a combination of resection, chemotherapy and radiotherapy. Due to the rarity of uterine RMS there is no accepted standard chemoradiotherapy regimen [5]. Prognosis is variable and highly dependent on the histological subtype and the stage of disease at presentation. Pleomorphic RMS has a poor prognosis whereas embryonal RMS has comparatively better survivorship with long-term survival rates of 90% reported in uterine-confined disease treated with resection and chemotherapy [6].

Differential Diagnosis List

Final Diagnosis

Rhabdomyosarcoma of the uterus.

URL:	https://www.eurorad.org/case/14371
DOI:	10.1594/EURORAD/CASE.14371
ISSN:	1563-4086