AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

Liposarcoma is a malignant tumor of mesenchymal origin in which the bulk of the tumor differentiates into adipose tissue. Liposarcoma is a common neoplasm of the soft tissues, and it affects middle-aged patients. Commonly affected sites include the thigh, gluteal region, retroperitoneum, leg, and shoulder area. Liposarcomas rarely arise from a preexisting lipoma. The clinical presentation depends on the site of the tumors, most of which are palpable masses.

On radiographs, findings in the soft-tissue mass are nonspecific. Frequently, fat is not detectable radiologically. In general, the more aggressive tumors demonstrate more radiopacity, whereas well-differentiated tumors have a greater fat content. Liposarcoma tumors are the most radiosensitive soft-tissue tumors.

Related eMedicine topics:
Liposarcoma [Dermatology]
Liposarcoma [Pediatrics: General Medicine]

Pathophysiology

Location and appearance

Liposarcoma is regarded as a tumor of adults.¹ It is only rarely found in areas in which most of the body fat is usually stored; liposarcoma should instead be considered a tumor of the large connective tissue spaces in which cells have retained a potential for lipogenesis. The principal sites of involvement are the intermuscular gliding spaces and the perivascular and subcoelomic regions. Most tumors occur in the lower limbs, particularly in the popliteal fossa, with a special preference for the adductor canal, the medial thigh, the shoulder area, and the retroperitoneal, perirenal, and mesenteric regions.

The most common intra-abdominal location is the posterior perirenal site, in which the tumor usually displaces the kidney medially and anteriorly. The tumor demonstrates a close relationship to the psoas muscle and the renal capsule, to which it usually adheres. Renal invasion is usually not seen, but the tumor commonly compresses the renal pelvis, and it may compress and obstruct the ureter. Occasionally, the tumor may infiltrate the mesentery or grow beneath the parietal peritoneum, invading the anterior or lateral abdominal wall.

Multiple, apparently independent tumors have been described in the retroperitoneum, mesentery, and omentum. Rarely, the site of origin may be in the pelvis; occasionally, a pelvic tumor may arise in the buttock, with subsequent pelvic invasion. For reasons that remain unclear, the left side of the retroperitoneum is involved more frequently, whereas in the lower limbs, the right leg is preferred. Almost all tumors are deep seated, and most tumors arise from large connective-tissue spaces between muscles and along vessels and nerves.

An origin in the subcutaneous tissues is unusual, and tumors typically reach a considerable size before they invade the subcutaneous tissues.¹ The only exceptions to this rule occur in the neck, face, and shoulders, where smaller tumors may invade the subcutaneous fat.

Retroperitoneal tumors may reach an enormous size; the largest tumor reported weighed 275 lb. The mean weight was reported to be 7800 g, with a mean diameter of 22 cm. The mean weight of a lower-limb liposarcoma was reported to be 1640 g, with a mean diameter of 11.2 cm.

The gross appearance of the tumor depends on the histologic type, degree of vascularity, presence of necrosis, and amount of mature fat and fibrous tissue. The tumor appears as a smooth, lobulated, or nodular mass, and in most instances, it is well encapsulated. However, the appearance of an encapsulated tumor may be misleading, because daughter nodules are often present around the main mass. Recurrent tumors are not as well encapsulated. Complete excision is not always possible because of the close association of the tumor with vital structures; therefore, the recurrence rate is high.

Histologic features

Histologically, liposarcomas are classified in distinct groups, as follows^{1, 2, 3, 4}:

• Myxoid type with intermediate differentiation - This is the most common histologic form of liposarcoma. Histologically, the tumors exhibit moderate-sized cells with variable cytoplasmic fat formation set in a myxoid background with a rich capillary network. However, this classic appearance is subject to considerable variation, particularly with regard to the cellularity and the degree of fat formation.⁵
• Well-differentiated liposarcoma and its variants - These lipogenic-type tumors represent the second largest group. Histologically, the tumors are represented by malignant lipoblasts; these lesions have a large amount of lipid and a scanty myxoid matrix. In 1 variant, components of well-differentiated and pleomorphic liposarcoma are combined in the same neoplasm. In another variety, distinct areas of well-differentiated liposarcoma and cellular spindle cell or pleomorphic sarcoma are present, without recognizable lipogenesis. Analogous to dedifferentiated chondrosarcoma, dedifferentiated liposarcoma is the suggested name for these cases.⁶
• Round cell type - This is composed of small, round cells that have a distinct acidophilic cytoplasm and dark, round-to-oval nuclei. Occasionally, lipoblasts are present. Mitoses are segregated into small clusters or pseudoglandular arrangements by traversing strands of connective tissue. The histologic findings in this cell type may mimic those of lymphoma and Ewing sarcoma; therefore, the demonstration of lipoblasts is important.
• Pleomorphic type - The least common form of liposarcoma, this tumor is highly undifferentiated and presents with mucin, marked cellular pleomorphism, and a paucity of lipid.

Causes

Multiple lipomatous tumors have been compared with and related to neurofibromatosis. In both entities, multiple subcutaneous tumors occur, and in both, a familial tendency is noted. The occurrence of benign and malignant tumors in patients with neurofibromatosis is not unusual. Concurrent benign and malignant tumors also occur in patients with multiple lipomatosis, although less frequently.

The role of trauma has been emphasized in several papers as a causative factor in liposarcoma; however, this causal relationship is difficult to assess because minor trauma is common. In one series, trauma preceded liposarcoma in 11% of patients (17% with the tumor in the lower extremity, 2% with the tumor in the retroperitoneum). In 10 of 11 patients, the tumor was of the myxoid type. In most of these patients, the trauma was minor, making the causal relationship doubtful. However, the development of a liposarcoma after severe trauma was sufficiently common to merit consideration in the same series.

The interval between trauma and the development of a liposarcoma has been quoted as 6-16 months. Despite the few reports that have appeared in the literature, proof of a causal relationship between trauma and the development of liposarcoma is still lacking.

Rare instances of liposarcomas that occurred after radiation exposure have been described.

Related eMedicine topics:
Ewing Sarcoma
Ewing Sarcoma and Primitive Neuroectodermal Tumors
Neurofibromatosis Type 1
Neurofibromatosis Type 2

Frequency

United States

Liposarcoma is the second most common primary retroperitoneal tumor; it represents 95% of all fatty retroperitoneal tumors and 14-18% of all soft-tissue sarcomas.

International

In Europe, the incidence of liposarcoma is the same as that in the United States.

Mortality/Morbidity

Mortality and morbidity rates depend on the site and histologic type of the liposarcoma, as follows⁷:

• Survival figures are better in patients with lower-extremity tumors and are worse in patients with retroperitoneal tumors. Median survival periods are 113 months with myxoid tumors, 119 months with well-differentiated tumors, 59 months with dedifferentiated tumors, and 24 months with pleomorphic tumors.
• Local recurrence is the rule with all cell types and is invariable with well-differentiated liposarcoma and its variants. Because the better-differentiated variants predominate, overall 5-year survival rates are 60-70%. Excision followed by radiation therapy (60-70 Gy) results in a more significant reduction in local recurrence than does excision alone.
• The rate of distant metastasis is not significantly related to the type of therapy or the presence of local recurrence.⁸ Well-differentiated tumors and myxoid tumors metastasize late or perhaps not at all, whereas 85-90% of round cell and pleomorphic tumors metastasize to the lungs, visceral organs, and serosal surfaces. A minority of patients with limb liposarcoma are treated with amputation.

Race

No race predilection is reported.

Sex

A slight male preponderance is described.

Age

Liposarcoma is primarily a tumor of adults.¹

• The youngest patient reported was aged 18 years, and the oldest patient was aged 80 years.
• The average age has been calculated variably at 42 years and 53 years, in 2 series.
• Patients with liposarcoma in the extremities are, on average, 5-10 years younger than patients with retroperitoneal tumors.

Anatomy

The retroperitoneum contains elements of a variety of tissue types, including fibrous tissues, fat, muscles, lymph nodes, lymphatics, nerves of the sympathetic nervous system, fascia, blood vessels, mesothelial tissue, and remnants of the embryologic urogenital ridge.

Tumors arising from the retroperitoneum can be divided into 5 categories, as follows:

• Mesothelial tumors, including liposarcomas
• Lymphomas
• Metastatic tumors
• Neural tumors
• Tumors of remnants of the urogenital ridge

Clinical Details

Clinically, the symptoms of liposarcoma are nonspecific and depend largely on the site of the tumor. The symptoms are indistinguishable from those of any other large, space-occupying tumor. Most symptoms develop as a result of displacement of the nerves and vessels or as a result of compression of adjacent organs or structures, such as the urinary outflow tract and the gastrointestinal tract.

A slowly increasing, well-circumscribed mass is the presenting manifestation in more than 90% of all patients with lower limb tumors. The mass is painful in only approximately 5% of the patients. The pain is mild to moderate, even when the tumor is closely attached to nerves. In as many as one quarter of patients, the first sign is the development of an inguinal hernia and/or venous compression (heralded as pitting edema of the legs). In approximately 2% of patients, pitting edema occurs in the lower limb.

With retroperitoneal tumors, diffuse and gradual abdominal enlargement is an initial symptom in just over 50% of patients. The abdomen may be tender on palpation in 25% of patients; however, the pain is rarely severe, instead usually being mild. The onset of sudden, severe abdominal pain is more a feature of large abdominal lipomas than of liposarcomas. Renal function is disturbed in most patients with retroperitoneal tumors. The kidneys may be displaced or malrotated, and usually, the ureters are anteriorly displaced, leading to features of obstructive uropathy, which leads to renal failure.

Despite an increasing abdominal girth, overall weight loss is a prominent feature in approximately 25% of patients. The contrast between emaciation and a large abdomen with a tumor may be striking.

Generalized weakness, lassitude, and fatigue are common. Nausea, vomiting, and constipation have been reported in approximately 5% of patients. Intermittent chills and fever may occur as a result of tumor necrosis, hemorrhage, or urinary tract infections.

Preferred Examination

Plain radiographs usually offer little except perhaps aid in confirming the presence of a soft-tissue mass. Ultrasonography is helpful in confirming the presence of a mass when doubt exists. The use of radionuclides has been anecdotal, but imaging with fluorine-18 fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) scanning holds promise.⁹

Computed tomography (CT) scanning plays an important role in the pre-operative evaluation of lipomatous and myxoid tumors of the soft tissue.¹⁰ Besides providing valuable morphologic information, CT scan findings help to some extent in the differentiation of various types of lipomatous tumors. Well-differentiated liposarcomas may be distinguished from other types of tumors on the basis of their largely lipomatous appearance. Gadolinium-enhanced magnetic resonance imaging (MRI) is important in differentiating myxoid liposarcomas from benign cystic tumors.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. 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 magnetic resonance angiography (MRA) scans.

As of late December 2006, the Food and Drug Administration (FDA) had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. 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. For more information, see the FDA Public Health Advisory or Medscape.

Fine-needle aspiration biopsy is a useful procedure and may enable tissue typing.^{11, 12, 13, 14}

Limitations of Techniques

Well-differentiated tumors are easily characterized as fat-containing masses, although the differentiation between a malignant tumor and a benign one may not be possible. Poorly differentiated tumors may be indistinguishable from other mesothelial tumors, lymphomas, metastases, and inflammatory masses.

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

Because myxoid tissue is present in many benign and malignant tumors, MRI may not enable a specific diagnosis of a liposarcoma. Moreover, 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.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Other Problems to Be Considered

Angiolipoma
Leiomyosarcoma
Lipoma
Round cell type - Ewing sarcoma and lymphoma
Spindle cell lipoma¹⁵

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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.

CT SCAN

Section 5 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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.

MRI

Section 6 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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.

ULTRASOUND

Section 7 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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 MEDICINE

Section 8 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Gallium-67 (⁶⁷Ga) 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 a ⁶⁷Ga scan. It appears that ⁶⁷Ga 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 (²⁰¹Tl) chloride revealed a radionuclide sensitivity of 81%, which is higher than that of ⁶⁷Ga imaging (68.8%).³³ Another study showed that technetium-99m (^99mTc) 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 that ^99mTc bleomycin and ^99mTc pentavalent dimercaptosuccinic acid (^99mTc[V]-DMSA) scanning can better localize liposarcomas than can ⁶⁷Ga 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

Section 9 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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.

INTERVENTION

Section 10 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Fine-needle aspiration biopsy is useful in the differential diagnosis of myxoid sarcoma, particularly myxofibrosarcoma, myxoid chondrosarcoma, and low-grade myxoid liposarcoma.^{11, 12, 13, 14}

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  A 67-year-old man presented with a slowly growing mass on the left side of his groin and with mild left leg claudication (same patient as in Images 2-5). The patient was a nonsmoker and was not diabetic. T1-weighted, coronal magnetic resonance imaging (MRI) shows a 5-cm, low–signal-intensity, lobulated mass in the left upper thigh.
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Media type:  MRI

Media file 2:  T2-weighted, coronal magnetic resonance imaging (MRI) scan of the left upper thigh in a 67-year-old man who presented with a slowly growing mass on the left side of his groin and with mild left leg claudication (same patient as in Images 1 and 3-5). The image shows a high–signal-intensity, lobulated, septate mass in the region of the groin.
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Media type:  MRI

Media file 3:  Contrast-enhanced, axial magnetic resonance imaging (MRI) scan of the upper thigh in a 67-year-old man who presented with a slowly growing mass on the left side of his groin and with mild left leg claudication (same patient as in Images 1-2 and 4-5). The image shows fairly intense tumor enhancement.
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Media type:  MRI

Media file 4:  Short-tau inversion recovery, turbo spin-echo, axial magnetic resonance imaging (MRI) scan of the left upper thigh in a 67-year-old man who presented with a slowly growing mass on the left side of his groin and with mild left leg claudication (same patient as in Images 1-3 and 5). The image shows fluid signal intensity within the tumor.
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Media type:  MRI

Media file 5:  Magnetic resonance (MR) angiogram of the leg vessels in a 67-year-old man who presented with a slowly growing mass on the left side of his groin and with mild left leg claudication (same patient as in Images 1-4). The image shows medial displacement and compression of the left femoral artery, superficial femoral artery, and profunda by the tumor, which resulted in the claudication.
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Media type:  MRI

Media file 6:  Moderately hypervascular tumor in the right upper thigh shows irregular, fine tumor vessels and areas of tumor stain (see also Image 7).
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Media type:  X-RAY

Media file 7:  Moderately hypervascular tumor in the right upper thigh shows irregular, fine tumor vessels and areas of tumor stain (see also Image 6).
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Media type:  X-RAY

Media file 8:  Sagittal, T1-weighted magnetic resonance imaging (MRI) scan in a 32-year-old woman presenting with a palpable mass above the left popliteal fossa. The image shows a low–signal-intensity, lobulated mass in the region of the Hunter canal (same patient as in Images 9-12).
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Media type:  MRI

Media file 9:  Axial, T1-weighted magnetic resonance imaging (MRI) scan in a 32-year-old woman obtained through a palpable mass above the left popliteal fossa. The image shows a low–signal-intensity, lobulated mass (same patient as in Images 8 and 10-12).
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Media type:  MRI

Media file 10:  Axial, T2-weighted magnetic resonance imaging (MRI) scan in a 32-year-old woman presenting with a palpable mass above the left popliteal fossa (same patient as in Images 8-9 and 11-12). The image shows a high–signal-intensity, lobulated mass.
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Media type:  MRI

Media file 11:  Fat-saturated magnetic resonance imaging (MRI) scan through the tumor in a 32-year-old woman presenting with a palpable mass above the left popliteal fossa (same patient as in Images 8-10 and 12). The image shows fluid signal intensity within the mass.
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Media type:  MRI

Media file 12:  Ultrasonogram in a 32-year-old woman with a mass above the left popliteal fossa (same patient as in Images 8-11) shows a hypoechoic (but solid) mass.
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Media type:  Image

Media file 13:  A 50-year-old man presented with a 6-month history of a dull ache over the right hypochondrium (same patient as in Image 14). An ultrasonogram (not shown) depicted a poorly defined, infiltrating, echogenic mass in the right hepatic lobe with shadowing. A nonenhanced, axial computed tomography (CT) scan shows a low fat-attenuating mass under the diaphragm; the mass displaces the liver to the left.
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Media type:  CT

Media file 14:  Hepatic angiogram in a 50-year-old man who presented with a 6-month history of a dull ache over the right hypochondrium (same patient as in Image 13). The image shows a hypovascular mass that displaces the liver medially. The mass was believed to represent a retroperitoneal liposarcoma; however, at laparotomy, the tumor was discovered to be intrahepatic. The histologic appearance was that of a high-grade liposarcoma infiltrating the diaphragm.
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Media type:  X-RAY

Media file 15:  A plain radiograph of a left femur demonstrates a large, soft-tissue mass projected over the medial aspect of the thigh (arrowheads). Small areas of radiolucency (asterisk) and calcification (arrow) are shown.
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Media type:

Media file 16:  Magnetic resonance imaging (MRI) scans (coronal, T1-weighted image and axial, T1-weighted image with fat saturation) show a soft-tissue mass of the posterior aspect of the thigh. It has a predominantly low T1 signal intensity except in its inferior portion, which has a high T1 signal intensity isointense to subcutaneous fat. Complete suppression is shown on the axial, T1-weighted image with fat saturation (asterisk).
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Media file 17:  Computed tomography (CT) scan of the left thigh shows a huge mass (arrows) with predominant fat attenuation. The central soft-tissue component (asterisk) and thick, internal septations are consistent with liposarcoma.
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Media type:

Media file 18:  Contrast-enhanced, axial computed tomography (CT) scan of an abdomen demonstrates a huge, intra-abdominal, fatty mass with a soft-tissue component (arrow) and thick septations. The mass displaces the descending colon and the left kidney posteriorly.
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Media type:

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

1. Springfield D. Liposarcoma. Clin Orthop Relat Res. Apr 1993;(289):50-7. [Medline].
2. Evans HL. Liposarcoma: a study of 55 cases with a reassessment of its classification. Am J Surg Pathol. Dec 1979;3(6):507-23. [Medline].
3. Matushansky I, Hernando E, Socci ND, et al. A developmental model of sarcomagenesis defines a differentiation-based classification for liposarcomas. Am J Pathol. Feb 29 2008;[Medline].
4. Murphey MD. World Health Organization classification of bone and soft tissue tumors: modifications and implications for radiologists. Semin Musculoskelet Radiol. Sep 2007;11(3):201-14. [Medline].
5. Downs-Kelly E, Goldblum JR, Patel RM, et al. The utility of fluorescence in situ hybridization (FISH) in the diagnosis of myxoid soft tissue neoplasms. Am J Surg Pathol. Jan 2008;32(1):8-13. [Medline].
6. Horvai AE, Schaefer JT, Nakakura EK, et al. Immunostaining for peroxisome proliferator gamma distinguishes dedifferentiated liposarcoma from other retroperitoneal sarcomas. Mod Pathol. Jan 18 2008;[Medline].
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Article Last Updated: Mar 12, 2008