What is the role of MRI 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

Answer

MRI typically reveals an intramuscular mass with heterogeneous signal intensity on all pulse sequences (see the images below). As with other soft-tissue neoplasms, the signal intensity pattern is nonspecific, usually low to intermediate on T1-weighted images and intermediate to high on T2-weighted images; low signal intensity of T1-weighted images and prominent high signal intensity on T2-weighted images may be a feature of myxofibrosarcoma/myxoid MFH, reflecting the high water content of these lesions. Other findings include the following:

  • Regions of prominent fibrous tissue (high collagen content) may demonstrate low signal intensity on both T1-weighted and T2-weighted images.

  • Calcification may present as foci of low signal on both T1-weighted and T2-weighted sequences.

  • Subacute hemorrhage should be considered when regions of high signal are noted on both T1-weighted and T2-weighted images.

  • Areas of necrosis demonstrate a signal pattern similar to that of fluid.

  • As with CT, solid components of MFH typically reveal nodular and peripheral enhancement.

  • Tumor margins appear relatively well defined on MRI; a low signal intensity margin may be observed, representing a pseudocapsule.

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.
T2-weighted MRI demonstrates the tumor much more c T2-weighted MRI demonstrates the tumor much more conspicuously.
Preinfusion T1-weighted MRI reveals a large mass. Preinfusion T1-weighted MRI reveals a large mass. Although slightly heterogeneous, the tumor is predominantly isointense to muscle.
T1-weighted MRI obtained following intravenous adm T1-weighted MRI obtained following intravenous administration of gadolinium reveals circumferential enhancement of the tumor (same patient as in the previous image).
T2-weighted MRI reveals heterogeneous signal of th T2-weighted MRI reveals heterogeneous signal of the malignant fibrous histiocytoma (same patient as in the previous image). Central low signal intensity may be the result of old blood products.
T2-weighted MRI obtained following gadolinium admi T2-weighted MRI obtained following gadolinium administration reveals heterogeneous enhancement of the malignant fibrous histiocytoma.
Preinfusion T1-weighted MRI of a patient with a me Preinfusion T1-weighted MRI of a patient with a medial left thigh mass proven at biopsy to represent a malignant fibrous histiocytoma. Although slightly heterogeneous, the mass is predominantly isointense to muscle.
Malignant fibrous histiocytoma. T2-weighted MRI re Malignant fibrous histiocytoma. T2-weighted MRI reveals predominantly increased signal intensity in the tumor mass (same patient as in the previous image).

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

The radiologist should keep in mind that the diagnosis of UPS is made using histopathology, not imaging; however, MRI remains invaluable for delineating tumor extent.


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