18
cytology of Soft Tissue, Bone, and Skin
Fig. 18.2 Myxoid liposarcoma. (A) Histologic section. Uniform population of round to oval-shaped cells present in a myxoid stroma associated with a
vascular network with a "chicken-wire” appearance (H&E x LP). (B) Smear. Myxoid background matrix, plexiform vascular network, cells with round to ovoid
nuclei (Papanicolaou x MP).
Interestingly, dedifferentiated liposarcomas have a better prog-
nosis than other types of pleomorphic sarcoma.
Key features of dedifferentiated liposarcoma
• Polymorphous population of round or spindle cells,
including multinucleated forms;
• Occasional lipoblasts; and
• Myxoid matrix and arborizing vascular structures
rarely seen.
Myxoid Liposarcoma
Myxoid liposarcoma is the second most common type of lipo-
sarcoma. The most common primary site is deep soft tissue of
the extremities. It is rare in the retroperitoneum and subcuta-
neous tissue. The peak age incidence is in the fourth and fifth
decades of life, but it can occur in patients younger than 20 years
old. Histologically, myxoid liposarcoma is characterized by a
uniform population of round to oval-shaped cells and a vari-
able number of small signet ring lipoblasts which are present
in a myxoid stroma associated with a vascular network with a
"chicken-wire" appearance (Fig. 18.2A). Usually, myxoid lipo-
sarcomas do not show nuclear pleomorphism, giant cells, abun-
dant spindle cells, or increased mitotic activity.40-42 Areas with
round cell morphology or hypercellularity are usually associ-
ated with a poor prognosis. When present, the round cell com-
ponent contains solid sheets of small round cells with high N/C
ratio, conspicuous nucleoli, and no myxoid stroma. The cyto-
logical features include myxoid background matrix, plexiform
vascular network, cells with round to ovoid nuclei (Fig. 18.2B),
and uni- or multivacuolated lipoblasts with scalloped nuclei
(Fig. 18.3). The cytological differential diagnosis of myxoid
liposarcoma includes other tumors with a prominent myxoid
component on FNAB such as myxoma, myxoid chondrosar-
coma, and chordoma. Smears of intramuscular myxomas have
lower cellularity and do not show any cytological atypia. The
pathologist should be careful with collections of macrophages
with intracellular droplets of lipid and/or mucin material which
can be misdiagnosed as lipoblasts. Myxoid chondrosarcoma
Fig. 18.3 Myxoid liposarcoma. Smear. Multivacuolated lipoblasts with
scalloped nuclei (May-Grunwald-Giemsa x MP).
are characterized by the presence of chondroid differentiation
and the myxoid material is metachromatic in the air-dried
Giemsa-stained slides.43 Chordomas have a different distribu-
tion (along the spine) and the presence of physaliphorous cells
and nuclear inclusions is highly suggestive of this entity. The
finding of arborizing vascular structures is not pathogromonic
of myxoid liposarcoma, because similar structures may also be
seen in myxoid chondrosarcomas. The demonstration of the
specific translocation t(12;16)(q13;p11) of myxoid liposarcoma
by FISH and/or the identification of the fusion gene product
CHOP-TLS can help to establish the diagnosis.44
Key features of myxoid liposarcoma
• Cells with round to ovoid nuclei;
• Uni- or multivacuolated lipoblasts with scalloped
nuclei;
• Myxoid background matrix; and
• Plexiform vascular network.
475
previous page 470 ComprehensiveCytopathology 1104p 2008 read online next page 472 ComprehensiveCytopathology 1104p 2008 read online Home Toggle text on/off