Fact-sheet: Liposarcoma
Updated on 04/19/2018 at 4:59 PM
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Definition
Liposarcoma is the most common malignant soft tissue tumor after malignant fibrous histiocytoma (former nomenclature) and accounts for 10 to 18% of all malignant soft tissue tumors.
Mesenchymal tumor composed of mature adipocytes but also immature adipocytes or lipoblasts
Predominates in males after the fifth decade
Clinical features
Generally a well-circumscribed, lobulated mass that remains asymptomatic for a long time, even when large.
The preferred sites of liposarcoma are mainly the proximal limbs, particularly the lower limb (notably the thigh), which is affected four times more often than the upper limb. The second most commonly affected site is the retroperitoneum.
CT
Well-differentiated liposarcoma typically contains more than 75% adipocytic cells.
The lesion has well-defined margins, negative density (below -60 Hounsfield units), and contains thick septa or even intralesional nodules.
MRI
The mass is hyperintense on T1- and T2-weighted images and hypointense on fat-suppressed sequences.
Certain morphologic features favor malignancy of the mass, in particular the presence of thick septa (greater than 2 mm in thickness) and the presence of nodular and soft tissue components
The imaging appearance of dedifferentiated liposarcoma is often quite similar to that of well-differentiated liposarcoma.
A feature suggestive of this diagnosis is its biphasic appearance, corresponding to the juxtaposition of: (1) a fatty component (similar to that of well-differentiated liposarcoma and to subcutaneous fat) (2) a non-lipomatous soft tissue component that shows nonspecific MRI behavior.
Dedifferentiation of liposarcoma may also be suspected when these soft tissue nodules appear in a lesion previously considered to be a well-differentiated liposarcoma.
Regarding myxoid liposarcoma, MRI shows a well-defined, homogeneous mass, overall hypointense on T1 but potentially showing small hyperintense foci reflecting the presence of fat within it. On T2, the lesion is hyperintense, corresponding to a high proportion of mucopolysaccharides within the myxoid matrix. Myxoid liposarcoma may quite often (20% of patients) take on a pseudocystic appearance.
Management
Liposarcomas, like other soft tissue sarcomas, are treated primarily with surgery. +
The main goal of surgery is to completely remove the tumor and prevent its recurrence.
The most reliable method is wide resection.
Classification
The WHO classification distinguishes four different groups of liposarcoma:
- well-differentiated
- dedifferentiated
- myxoid
- pleomorphic
Differential diagnosis
Conventional lipoma