Soft tissue sarcomas are rare mesenchymal tumours, which originate in
non-epithelial connective tissue sources; liposarcomas are the most
common soft tissue sarcomas.
histopathologic subgroups of liposarcomas have been identified, as
follows: well differentiated; myxoid; round cell; dedifferentiated;
and pleomorphic variants.
Myxoid liposarcoma is
the most common subtype of liposarcoma, representing approximately
one-third of all liposarcomas.
Myxoid soft-tissue sarcomas encompass a heterogeneous group of rare
tumours characterized by a marked abundance of mucoid/myxoid
clinicopathological entities in this group are myxoid liposarcoma,
low-grade fibromyxoid sarcoma, extraskeletal myxoid chondrosarcoma,
myxofibrosarcoma, myxoinflammatory fibroblastic sarcoma, and myxoid
working group of the World Health Organization (WHO) for
classification of tumours of soft-tissue and bone combined myxoid and
round cell liposarcomas under myxoid liposarcoma.
Liposarcomas may arise in any fat region. Myxoid liposarcoma occurs
predominantly in the deep soft-tissues of lower extremities and
rarely occur in the retroperitoneum.
incidence of myxoid liposarcomas is high during the fourth and fifth
decades of life, and there is no gender predilection.
Pure myxoid liposarcoma is considered low-grade and has a 5-year
survival rate of 90%.
myxoid liposarcomas containing a greater than 5% round cell component
is considered high-grade and has a worse prognosis.
contrast to other soft-tissue sarcomas, myxoid liposarcoma tends to
metastasize to unusual sites such as retroperitoneum, opposite
extremity, and bone.
Histologically, pure myxoid liposarcomas is composed of primitive
mesenchymal cells in a myxoid matrix, often featuring mucinous pools.
are most often univacuolated, small, and tend to cluster around
vessels or at the periphery of the lesion.
delicate plexiform capillary vascular network ('crow's feet' or
'chicken wire pattern' ) is present and provides
an important clue for distinguishing myxoid liposarcomas from
subset of myxoid liposarcoma shows histological progression to
hypercellular or round cell morphology. The round cell areas are
characterized by solid sheets of primitive round cells with a high
nuclear/cytoplasmic ratio and a prominent nucleolus.
Myxoid liposarcoma is characterized by a recurrent translocation t(12;16)(q13;p11)
in more than 90% of cases.
Most cases of myxoid liposarcomas are one of three different
FUS-DDIT3 fusion transcript types,
including varying portions of FUS.
The FUS-DDIT3 fusion transcript
type does not appear to have a significant impact on clinical outcome.
(16) Myxoid liposarcoma
with a type 1 EWSR1-DDIT3 fusion
transcript may show more favorable clinical behavior than those with
other types of fusion transcripts.
Several receptor tyrosine kinases (RTKs) are highly expressed in
myxoid liposarcoma , including RET, MET, and IGF1R.
Purely myxoid lesions are characterized by a 5-year survival rate of
approximately 70%, which drops to approximately 20% in the case of
round cell tumours.
Patients who present with multifocal disease have a poor prognosis and
the presence of necrosis and p53 overexpression have been found to be
independent predictors of poor prognosis.
Local recurrence has
been reported with an unusually high incidence of soft tissue and bone
metastases to the lung.