What is the role of CT in the workup of pleomorphic sarcoma (malignant fibrous histiocytoma) of soft tissue?

Updated: Nov 07, 2018
  • Author: Gregory Scott Stacy, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

On CT images, UPS lesions are well-circumscribed, multinodular, or infiltrating masses of soft-tissue attenuation. Undifferentiated pleomorphic sarcomas are often large at the time of diagnosis and invade adjacent anatomic structures. Centrally within the tumor, areas of low-attenuation necrosis, hemorrhage, or myxoid change can be seen. The tumor may appear cystic with a rim of peripheral enhancement when marked intralesional hemorrhage is present. [1]

Calcification from osseous or chondroid metaplasia occurs in approximately 16% of cases. Calcifications may be small and punctate in a speckled pattern or coarse and chunky. After administration of intravenous contrast material, the enhancement pattern is variable, although regions of marked contrast enhancement and large intratumoral vessels may be seen. Hemoperitoneum from tumoral hemorrhage has been reported. [1]  

Fat attenuation is not observed in the tumors; this fact can be useful in distinguishing undifferentiated pleomorphic sarcoma from some well-differentiated liposarcomas. [13]

Retroperitoneal tumors manifest as heterogeneous masses with areas of hemorrhage and/or necrosis and occasionally focal or diffuse coarse calcifications (approximately 10%); the tumors may invade the abdominal musculature but do not invade the renal veins or inferior vena cava. [12, 14, 15]

(See the images below.)

Transverse CT image following enhancement with int Transverse CT image following enhancement with intravenous contrast shows a heterogeneous and mildly enhancing soft tissue mass in the posteromedial right thigh.
T2-weighted MRI reveals a hyperintense mass within T2-weighted MRI reveals a hyperintense mass within the posteromedial right thigh (same patient as in the previous image). The mass proved to be a malignant fibrous histiocytoma.
CT reveals a mass within the anterior compartment CT reveals a mass within the anterior compartment musculature of the left thigh. The malignant fibrous histiocytoma is only slightly hypodense to muscle and conceivably could be overlooked.
T2-weighted MRI demonstrates the tumor much more c T2-weighted MRI demonstrates the tumor much more conspicuously.

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