Liposarcoma

General characteristics

A liposarcoma is a malignant soft tissue neoplasm that contains cells with lipoblastic or lipocytic differentiation. It is the second most common malignant soft tissue tumor after malignant fibrous histiocytoma.

Epidemiology

Its peak incidence is between 50 and 60 years of age, and it is rare before 20 years of age.

Location

Liposarcomas are most common in the extremities, especially the thigh, and in the retroperitoneum. Liposarcomas can be divided into four groups on the basis of their histologic characteristics:

  • well-differentiated
  • myxoid,
  • round cell,
  • pleomorphic.

Imaging

The CT or MR. appearance depends on the degree of differentiation. The portions of the tumor that contain fat demonstrate a low amnuation coefficient on CT scans and have high signal intensity on TI-weighted MR images. The nonlipomatous portions of the tumor have a higher attenuation coefficient than fat on CT scans; their signal intensity is similar to that of muscle on TI-weighted MR images and is higher than that of fat on T2- weighted images.

A well-differentiated liposarcoma and an atypical lipoma can share the same characteristics on both CT and MFU, making differentiation between these two entities difficult. More aggressive liposarcomas may contain no fat that is detectable by either CT or MRI. In these cases, the appearance of the tumor is indistinguishable from that of other malignant soft tissue tumors.