eMedicine Specialties > Radiology > Musculoskeletal

Liposarcoma, Soft Tissue: Imaging

Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia
Coauthor(s): Muthusamy Chandramohan, MBBS, DMRD, FRCR, Consultant Radiologist, Bradford Teaching Hospitals, UK; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Fahad Ogla Alkubaidan, MBBS, SSCR, Associate Consultant, Musculoskeletal Radiology, Deputy Program Director, Residency Training Program, King Abdulaziz Medical City (KAMC), Riyadh, Saudi Arabia
Contributor Information and Disclosures

Updated: Mar 12, 2008

Radiography

Findings

Radiographic findings are seldom diagnostic, and the images may demonstrate a nonspecific, soft-tissue mass. Frequently, no fat is detectable. Rarely, calcification is present.

Abdominal radiographs in patients with retroperitoneal tumors may reveal a soft-tissue – displacing, gas-filled structure and effacement of the normal fat planes.

Contrast-enhanced studies of the gastrointestinal tract may show displacement of the stomach, small bowel, or colon, depending on the location of the tumor.

Intravenous urography may show renal or ureteric displacement; rarely, hydronephrosis is demonstrated.

Degree of Confidence

The sensitivity and specificity of radiographs are low in liposarcoma.

False Positives/Negatives

Inflammatory masses and other types of benign and malignant tumors can have a similar appearance.

Computed Tomography

Findings

CT scans demonstrate 3 distinct patterns, as follows:

  • An enhancing, solid, inhomogeneous, poorly defined, infiltrating mass
  • A mixed-pattern tumor with foci of fat interspersed in high-attenuating tissue
  • A pseudocystic water-density tumor.

Liposarcomas of the myxoid type, the mixed myxoid and round cell type, the round cell type, and the pleomorphic type are usually poorly defined, with attenuation values of 12-38 HU and varying degrees of contrast enhancement.16,17 Calcification is detectable in as many as 12% of the tumors.

Occasionally, the mass may appear inhomogeneous, with areas of low-attenuating, fatty components.18,19 Fatty components may be demonstrated better with planar tomography.

Degree of Confidence

CT scanning plays an important role in the pre-operative evaluation of lipomatous and myxoid tumors of the soft tissue.20 Besides providing valuable morphologic information, CT scanning helps to some extent in differentiating various types of lipomatous tumors.21,22 CT scanning is useful in the determination of the tumoral response to radiation therapy or chemotherapy; it is also invaluable in the detection of tumor recurrence.

False Positives/Negatives

Malignant fibrous histiocytoma, leiomyosarcoma, and desmoid tumors may have an appearance that is indistinguishable from that of liposarcoma, particularly liposarcoma of the myxoid, mixed myxoid and round cell, round cell, or pleomorphic type.

Magnetic Resonance Imaging

Findings

Most liposarcomas appear well defined on MRI scans, mostly with lobulated margins.23 Well-differentiated liposarcomas are made up primarily of fat and have septations or nodules; these neoplasms are hyperintense on T2-weighted images.16,24 After the administration of contrast material, well-differentiated liposarcomas may enhance minimally or not at all.

A spectrum of abnormal MRI findings may occur in the myxoid type, depending on the quantity of fat and myxoid material that is present, on the degree of cellularity and vascularity, and on whether or not necrosis exists.25 Most myxoid tumors have linear or lacy, amorphous foci of fat.26 Some myxoid tumors may appear cystic on nonenhanced MRI scans, but they are usually enhancing after the administration of contrast agents.27

Pleomorphic tumors show a markedly heterogeneous internal structure and moderate contrast enhancement. The malignancy grade is believed to increase in parallel with tumor heterogeneity and contrast enhancement.

Degree of Confidence

Well-differentiated liposarcomas may be distinguished from other types of tumors on the basis of their largely lipomatous appearance.28 Gadolinium-enhanced imaging is important in differentiating myxoid liposarcomas from benign cystic tumors.

False Positives/Negatives

Myxoid tissue is present in many benign and malignant tumors, including extraskeletal myxoid chondrosarcomas, intramuscular myxomas, ganglia, and myxoid, malignant fibrous histiocytomas, in addition to myxoid liposarcomas. Any lesion consisting of edema, an extracellular matrix with a high level of mucopolysaccharide, hyaline cartilage content, and necrosis may appear cystic on MRI scans.

Ultrasonography

Findings

Ultrasonography is helpful in confirming the presence of a mass.29,30 Liposarcomas are usually hyperechoic. Retroperitoneal liposarcomas are highly reflective, although this feature may be absent when the tumor is poorly differentiated.

The finding of a solid retroperitoneal mass that demonstrates a heterogeneous echo pattern with an echo-poor center usually suggests a sarcoma. The central echo-poor area is usually the result of hemorrhage or necrosis (because the tumors tend to outgrow their blood supply).

A well-differentiated, peripheral liposarcoma is usually hyperechoic and may be indistinguishable from a lipoma; however, Doppler ultrasonography studies reveal that a liposarcoma is more vascular than a lipoma.

The remaining 3 varieties of liposarcoma appear as a heterogeneous, soft-tissue mass with no distinguishing characteristics.

Degree of Confidence

Confirming the retroperitoneal origin of a tumor is not always possible with ultrasonography. However, some characteristic features may be helpful in locating the tumor's origin. These include anterior displacement of the pancreas, abdominal aorta, inferior vena cava, kidneys, and ascending or descending colon. The benign or malignant nature of retroperitoneal tumors cannot be determined by using ultrasonography.

False Positives/Negatives

Vascular tumors, such as hemangiopericytomas, can be highly reflective, presumably because of the numerous tissue interfaces with multiple vascular walls. Distinguishing poorly differentiated liposarcomas from other types of retroperitoneal or peripheral masses is not always possible. A peripheral well-differentiated liposarcoma may have the appearance of a lipoma.

Nuclear Imaging

Findings

Gallium-67 (67 Ga) citrate scintigraphy scanning was evaluated in one series of 90 patients with soft-tissue tumors of the limbs.31 Positive findings were found in 78% of patients with malignant tumors, 25% of patients with benign lesions, and 31% of patients with other types of lesions. Distinguishing liposarcoma from lipoma appeared to be possible by means of a67 Ga scan. It appears that67 Ga scanning can play an important part in the evaluation of patients presenting with a primary or metastatic soft-tissue sarcoma.32 67 Ga scanning may also have a role in imaging liposarcoma recurrence.

A study of 78 patients with malignant soft-tissue sarcoma who were evaluated with thallium-201 (201 Tl) chloride revealed a radionuclide sensitivity of 81%, which is higher than that of67 Ga imaging (68.8%).33 Another study showed that technetium-99m (99m Tc) pertechnetate can potentially aid in the localization of malignant soft-tissue tumors and may be useful in their evaluation.34,35

Another small study showed that99m Tc bleomycin and99m Tc pentavalent dimercaptosuccinic acid (99m Tc[V]-DMSA) scanning can better localize liposarcomas than can67 Ga imaging.36 In another study, 17 patients with proven or suspected local recurrences of a soft-tissue sarcoma were examined with FDG-PET scanning.37 Recurrence was revealed in 93% of patients. Still another small study showed that PET scanning can be used to image and evaluate the metabolic activity of human musculoskeletal tumors.

Degree of Confidence

Experience is insufficient to assess the degree of confidence in the diagnosis of liposarcoma with radionuclides.

False Positives/Negatives

In an FDG-PET study of 17 patients, the tumor was not depicted in 1 individual, a patient with a recurrent, low-grade liposarcoma.37

Angiography

Findings

Liposarcomas are usually hypovascular to moderately vascular, and they cause displacement of the major vessels, particularly the inferior vena cava.38 Moderately hypervascular liposarcomas may show irregular, fine tumor vessels and areas of tumor stain. Venous filling may occur early, and the veins may be dilated and tortuous. Displacement of the kidneys and arteries is seen in all except very small retroperitoneal tumors.

Degree of Confidence

Angiography may be useful for pre-operative planning, intra-arterial infusion, and/or transcatheter embolization.

False Positives/Negatives

Angiography cannot help in the differentiation of liposarcomas from other types of sarcomas. Benign and malignant retroperitoneal tumors can be avascular.

More on Liposarcoma, Soft Tissue

Overview: Liposarcoma, Soft Tissue
Imaging: Liposarcoma, Soft Tissue
Follow-up: Liposarcoma, Soft Tissue
Multimedia: Liposarcoma, Soft Tissue
References
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Further Reading

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Keywords

soft-tissue liposarcoma, soft-tissue tumors, soft-tissue neoplasms, soft-tissue lesions, mesenchymal malignancy, mesenchymal tumor, adipose-tissue tumor, soft-tissue mass, tumors of large connective tissue spaces, retroperitoneal tumors, myxoid tumors, round cell tumors, well-differentiated tumors, pleomorphic tumors

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Contributor Information and Disclosures

Author

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia
Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England
Disclosure: Nothing to disclose.

Coauthor(s)

Muthusamy Chandramohan, MBBS, DMRD, FRCR, Consultant Radiologist, Bradford Teaching Hospitals, UK
Disclosure: Nothing to disclose.

Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute
Sumaira MacDonald, MBChB, PhD, MRCP, FRCR is a member of the following medical societies: British Medical Association, Royal College of Physicians, and Royal College of Radiologists
Disclosure: Nothing to disclose.

Fahad Ogla Alkubaidan, MBBS, SSCR, Associate Consultant, Musculoskeletal Radiology, Deputy Program Director, Residency Training Program, King Abdulaziz Medical City (KAMC), Riyadh, Saudi Arabia
Disclosure: Nothing to disclose.

Medical Editor

Giuseppe Guglielmi, MD, Associate Professor of Radiology, Department of Radiology, Scientific Institute Hospital
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Murali Sundaram, MBBS, FRCR, FACR, Consulting Staff, Department of Diagnostic Radiology, The Cleveland Clinic Foundation
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Felix S Chew, MD, MBA, EdM is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

 
 
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