CASE 8155 Published on 01.05.2010

Leiomyosarcoma of the rectum

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Hasni Bouraoui I, Jemni H, Ben Jazia E, Mazhoud J, Daadoucha A, Slama A,Tlili Graeiss K

Patient

76 years, female

Clinical History
76 year old female presents with painful defecation, rectal bleeding and iron deficient anaemia. Lower GI endoscopy revealed a rectal mass.
Imaging Findings
76 year old female presented with painful defecation, rectal bleeding and iron deficient anaemia. A large and mass was palpated on digital rectal examination and in lower GI endoscopy. Biopsy was perfomed and histological examen confirmed diagnosis of rectal leiomyosarcoma. MRI was performed to evaluate tumoral extention (Fig. 1-4). Because of large size and extent of tumor and advanced age of patient, she was treated by left colostomy and palliative radiotherapy.
Discussion
Most rectal tumors are of epithelial origin. Only a small number of mesenchymal tumors originate from the smooth muscle cells in the rectal wall. Leiomyosarcoma of the colon, rectum, and anus comprise less than 0.1% of all colo-rectal malignancies and may have a submucosal, subserosal or intraluminal location (1). They are typically large, lobulated masses and may undergo tumor hemorrhage or necrosis. Rectal leiomyosarcomas have a predominantly exophytic shape and may mimic tumors arising from neighbouring viscera such as prostate (1,2). Larger exophytic lesions can cause an extrinsic mass effect on adjacent viscera. Since they grow within the rectal wall, the symptoms are usually few or late, leading to delays in diagnosis: Leiomyosarcoma is often locally extensive at the time of diagnosis (3) and has a high propensity for local recurrence and metastases especially to the liver and lungs (4). Wide surgical excision allows the best chance of cure (2).
On endorectal ultrasound, leiomyosarcoma appears as a heterogeneously hypoechoic mass with central cystic areas due to necrosis and hemorrhage (4). The exact organ of origin can be difficult to determine with larger tumours. CT shows a large circumscribed, heterogeneous, hypodense mass with variable contrast enhancement and areas of cystic necrosis (4). On MRI, leiomyosarcoma appears as a large mass with low signal on T1-weighted images, intermediate signal on T2- weighted images, and shows variable contrast enhancement. Cystic necrotic areas appear as high signal on T2-weighted images (2).
Differential diagnosis includes the other rectal neoplasms. Lymphoma usually presents with excavation or as a grossly ulcerated mass with no extra-rectal component, accompanied by lymphadenopathy. Adenocarcinoma is characterized by an annular constricting lesion with mucosal destruction and ulceration and often invasion of the perirectal fat (3).
Imaging is of importance in revealing and characterizing rectal leiomyosarcomas (2).
Differential Diagnosis List
Leiomyosarcoma of the rectum
Final Diagnosis
Leiomyosarcoma of the rectum
Case information
URL: https://www.eurorad.org/case/8155
DOI: 10.1594/EURORAD/CASE.8155
ISSN: 1563-4086