Liposarcoma
Epidemiology:
Common sites:
Gross features:
Histologic features:
- well-differentiated (see atypical
lipomatous tumour)
- dedifferentiated liposarcoma:
- has a transition from well-differentiated liposarcoma to non-lipogenic
sarcoma
- at least several mm in diameter
- myxoid
liposarcoma (intermediate grade by definition):
- not circumscribed
- uniform round to oval primitive non-lipogenic mesenchymal cells
- more cellular than myxoma
- uniform nuclei
- variable number of small signet-ring lipoblasts
- prominent myxoid
stroma
- characteristic branching vascular pattern
- typically lacking:
- nuclear pleomorphism
- giant tumour cells
- prominent areas of spindling
- significant mitotic activity
- pleomorphic liposarcoma:
- pleomorphic, high-grade
- pleomorphic lipoblasts in varying amount
- no areas of well-differentiated or other line
of differentiation present
- mixed-type:
- shows features of more than one of the above
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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S-100
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HMB-45 (neg)
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Molecular features:
- Dedifferentiated:
- Similar to WD
- Most with one or more ring
- Additional aberrations (75%)
- Polyploidy chromosome numbers (50%)
- Some have complex karyotypes
- Multiple numerical and unbalanced
rearrangements mostly
- myxoid
and round cell:
- t(12;16) in most cases (fusion gene: CHOP/TLS)
Other features:
- myxoid
type is intermediate malignancy
- round cell and pleomorphic variants are
aggressive
References:
- Robbins 2005
- WHO book 2002
- Heim & Mitelman,
Cancer Cytogenetics, 3rd Ed.