Keywords

Definition

  • An exceedingly rare malignant intraosseous neoplasm, constituted by adipose cells, which can also arise on the surface of bone.

Etiology

  • Unknown.

  • It may arise from preexisting lipomas.

Epidemiology

  • Liposarcoma of bone is an exceedingly rare tumor.

Age

  • It can be seen at any age but is more common in adults.

Sex

  • There is a slight male predominance.

Sites of Involvement

  • Almost all cases reported are in the long bones, especially femur and tibia.

Clinical Symptoms and Signs

  • Pain and the presence of a mass are the usual symptoms.

  • Pathological fracture may occur.

Image Diagnosis

  • Radiographs show a lucent mass that may or may not present well-defined margins, including cortical permeation.

  • CT and MRI of the tumor show features characteristic of fat tissue.

Image Differential Diagnosis

  • The nonspecific image findings of liposarcoma in bone can be seen in various other benign and malignant bone lesions.

Pathology

Gross Features

  • The cut surface shows a lobulated, yellow to white, and soft or firm lesion, with well- or poorly defined margins. It is usually a large lesion.

  • Some lesions may present myxoid, mucinous features.

Histological Features

  • Similar to soft tissue variants of liposarcomas:

    • Atypical lipomatous tumor/well-differentiated liposarcoma.

      Neoplastic tissue is very similar to normal fat. Atypical nuclei may be seen mostly in or near the spindle cell septae that traverse the neoplasia. A few lipoblasts are also seen.

    • Dedifferentiated liposarcoma

      Abrupt transition from low-grade lipogenic area to high-grade non-lipogenic morphology within a well-differentiated liposarcoma is seen. May have heterologous elements.

    • Myxoid liposarcoma

      It may be constituted by two neoplastic tissue patterns, a richly arborizing vascularized myxoid pattern and a round cell pattern. Patterns may be seen alone or in variable mixture in a particular tumor.

    • Pleomorphic liposarcoma

      Highly anaplastic fat cells characterize this variant.

Pathology Differential Diagnosis

Lipoma

  • It may be difficult to differentiate from well-differentiated liposarcoma in a limited sample.

Ancillary Techniques

  • MDM2/CDK4 are usually positive together or individually in liposarcomas. Pleomorphic liposarcomas differ from the dedifferentiated variant by expressing only one marker.

Genetics

  • Supranumerary ring or long marker chromosomes in well-differentiated liposarcomas.

  • Translocation t(12;16) is common in myxoid/round liposarcoma. Fusion of DDIT3 (CHOP) and FUS (TLS) genes. Translocation t(21;22) rarely.

  • Amplification of 12q14.2–21.2 includes the HMGA2 and MDM2 gene regions.

  • Various aberrations of 12q13–15 were described in lipomas.

  • Pleomorphic liposarcomas present complex karyotypes.

  • Amplification of 1q21.2–31.2 was described in a parosteal liposarcoma.

  • Abnormalities in the AKT genes were found to correlate with clinicopathological profile of tumors.

Prognosis

  • Well-differentiated and myxoid liposarcoma, the two most common types, have a more favorable prognosis than the other histological types.

Treatment

  • Wide resection or amputation

Images

See Figs. 42.1, 42.2, 42.3, 42.4, 42.5, 42.6, and 42.7 for illustrations of liposarcoma of bone.

Fig. 42.1
figure 1

(a, b) Radiographs of a liposarcoma of the femur. Uncharacteristic lucent mass in the medullary compartment with some endosteal scalloping and undefined limits

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Fig. 42.2
figure 2

CT scan of surface liposarcoma of the proximal femur. Well-circumscribed lucent lesion distorting the host bone external shape

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Fig. 42.3
figure 3

Low-power microscopic view of well-differentiated liposarcoma

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Fig. 42.4
figure 4

Medium-power microscopic view of well-differentiated liposarcoma. Atypical cells are more easily found in the spindle cells septae of the lesion

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Fig. 42.5
figure 5

High-power microscopic view of well-differentiated liposarcoma. There may be only a few atypical cell nuclei. Multivacuolated adipocytes and lipoblasts are also seen

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Fig. 42.6
figure 6

High-power microscopic view of well-differentiated liposarcoma. Multiple atypical nuclei in adipocyte

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Fig. 42.7
figure 7

Medium-power microscopic view of pleomorphic liposarcoma

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