Heterogeneous lesion composed of adipocytes, inflammatory cells and atypical stromal cells
Adipocytes: sheets and nests of polygonal cells; abundant clear cytoplasm with mild variability in size and shape; eccentric small monomorphic nuclei
Inflammatory cells: admixture of lymphocytes, plasma cells, and histiocytes
Stromal cells: spindle-polygonal cells; eosinophilic cytoplasm; ovoid-round nuclei with prominent nucleoli, occasional multinucleation, moderate pleomorphism and inconspicuous mitotic activity
IHC: CDK4, MDM2
FISH: MDM2 amplified
The subtypes of well-differentiated liposarcoma often show morphologic overlap
Sheets of polygonal cells
Abundant clear cytoplasm with mild variability in size and shape; rare multivacuolation
Peripherally located small monomorphic nuclei
FISH: MDM2 amplified
Sheets of polygonal cells
Abundant clear cytoplasm with mild variability in size and shape; rare multivacuolation
Peripherally located small monomorphic nuclei
FISH: MDM2 amplified
Infiltrative sheets of polygonal cells
Abundant clear cytoplasm with mild variability in size and shape; rare multivacuolation
Peripherally located small monomorphic nuclei
Background skeletal muscle has atrophy and reactive changes
FISH: MDM2 amplified
Sheets of polygonal cells and loose fascicles of spindle cells
Polygonal cells have abundant clear cytoplasm with mild variability in size and shape and rare multivacuolation; peripherally located small monomorphic nuclei
Spindle cells have pale eosinophilic cytoplasm; hyperchromatic ovoid nuclei with mild pleomorphism; delicate collagenous stroma
Polygonal cells with abundant eosinophilic cytoplasm and round, often binucleated, nuclei can often be found interspersed and/or lurking in the walls of vessels
FISH: MDM2 amplified
There is considerable overlap with so-called "low-grade" dedifferentiation (the latter is differentiated on low-power examination as lacking a significant interspersed lipogenic component)