Represents 40-45% of all liposarcoma.
Commonly occurs in the retroperitoneum or the limbs and rarely in the
spermatic cord and the mediastinum.
The alternative terms
'atypical lipoma'
and 'atypical
lipomatous tumour'
have
been suggested by different authors. The behaviour of these lesions
is substantially different depending on the location of the tumour.
Tumour in somatic soft tissue may recur but is incapable of distant
metastasis and there is no tumour related death. Tumour in
retroperitoneum have a high incidence of recurrence. The recurrent
tumours may have 'dedifferentiated' appearance. Some of these patients
die as a result.
GROSS IMAGE
(pathweb)Subtypes according to
histopathological features:
1. Adipocytic (lipoma like)
2. Sclerosing
3. Inflammatory
4. Spindle cell
1.Adipocytic(Lipoma like )-
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;
2
;
3
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4
Large well cicumscribed and coarsely lobulated tumour.
Microscopically, there are mature adipocytes showing variation in
cell size. Focally nuclear atypia is evident.
In areas individual nuclei are compressed to crescentic shape.Some hyperchromatic stromal cells are present. Lipoblasts may or may not be
present.
Note: Presence of
lipoblasts is not diagnostic of liposarcoma. Lipoblasts are noted in
benign adipocytic tumours, eg.
chondroid
lipoma,
lipoblastoma,
pleomorphic lipoma
.
2. Sclerosing-
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; 3
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These are relatively pale and firm lesions occur most frequently in
the retroperitoneum and the paratesticular region.
Microscopically , there are scattered hyperchromatic stromal cells,
multivacuolated lipoblasts set in a collagenous backround. Foci of
atypical lipomatous elements are noted.
3.Inflammatory-
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1 ; 2 ;
3 ;
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5
There is a dense chronic inflammatory infiltrate almost obscuring the
lipogenic areas. Prominent aggregates of lymphoid cells and plasma cells are noted simulating inflammatory pseudotumour.
4. Spindle cell- IMAGE LINK 1
; 2
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There is proliferation of bland spindle cells in a fibrous or myxoid
backround together with atypical lipomatous component including
lipoblasts. The differential diagnosis include:
malignant peripheral nerve
sheath tumour, spindle cell lipoma
,
neurofibroma (S100 positive),
dermatofibrosarcoma
protuberans (diffuse CD34 positive)
, well differeniated sclerosing liposarcoma
and
low grade fibromyxoid sarcoma.
Cytogenetics-
Ring or long marker chromosome derived from q13-15
region of chromosome 12. |
