Which histologic findings are characteristic of liposarcoma?

Updated: Mar 18, 2020
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
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Answer

The recognition of lipoblasts is the key finding in the diagnosis of liposarcoma. A lipoblast has the ability to produce and accumulate non–membrane-bound lipid within its cytoplasm. The key morphologic features are well-demarcated cytoplasmic lipid that shifts, causes indentations in an irregular hyperchromatic nucleus, and creates a characteristic scalloping of the nuclear membrane.

The stage and further differentiation into 1 of the 4 major types affect the prognosis.

Well-differentiated liposarcomas usually contain a predominance of mature fat cells with relatively few, widely scattered lipoblasts. A misdiagnosis of lipoma can result from inadequate sampling. In the sclerosing subtype of a well-differentiated liposarcoma, collagen fibrils that encircle fat cells and lipoblasts make up a prominent part of the matrix.

Myxoid liposarcoma, the most common type, is diagnosed by the observation of a delicate plexiform capillary network that is associated with both primitive mesenchymelike cells and a variable number of lipoblasts. The stroma contains a large proportion of myxoid ground substance (ie, hyaluronic acid), in which numerous microcysts may form.

In the round-cell type, lipoblasts are interspersed among sheets of poorly differentiated round cells.

Poorly differentiated pleomorphic liposarcoma is recognized by a mixture of bizarre, often multivacuolated lipoblasts and atypical stromal cells, many of which contain highly abnormal mitotic figures. Hemorrhagic and necrotic areas are common. Lipoblasts are present.


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