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Leiomyosarcoma
of the soft tissue is divided into following groups:
1. Cutaneous
(primary or secondary); 2. Subcutaneous and deep soft tissue; 3.
Intra-abdominal 4. Vascular.
Leiomyosarcoma
commonly occurs in the fifth to seventh decade. Cutaneous variant usually
occurs in younger adults.
1. Cutaneous
leiomyosarcomas
are commonly
located on the extensor surfaces of the extremities, particularly lower
legs. Rarely these may occur on the scalp, upper lips, nipple and scrotum.
Grossly the tumour is usully less than 2 cm in diameter. External surface
may display areas of discolouration, umbilication and ulceration. Cut
surface reveals a grayish white whorled appearance. Local recurrences may
occur. There is usually no evidence of metastasis.
Secondary leiomyosarcomas arise from primary retroperitoneal or uterine
leiomyosarcoma and present as dermal and subcutaneous nodules on the scalp
or back.
2.
Subcutaneous leiomyosarcoma
are commonly located on the thigh. These are larger lesions and grow
rapidly. Recurrence occurs in 50%-70% cases. Distant metastasis to lung ,
liver and bone occur in about 50% cases.
3.
Intra-abdominal leiomyosarcomas
are located in
the retroperitoneum, mesentery and omentum. These are large lesions and
often unresectable.The mean size of the tumour is about 16 cm. The tumour
presents as a fleshy gray white mass with foci of hemorrhage and necrosis.
Cystic degeneration may be present. Some tumours macroscopically resemble
leiomyoma on cut sections.
4. Vascular
leiomyosarcoma
occur in
large veins ( inferior vena cava or larger veins of leg - saphenous, iliac
and femoral) . Macroscopically nodular or polypoid masses are firmly
attached to the vessel. The tumour spreads along the surface of the blood
vessel.
PATHOLOGICAL
FEATURES:
IMAGE LINKS: (ESCOP)
Low grade leiomyosarcoma:
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High grade leiomyosarcoma: Image1
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Image3;
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Myxoid leiomyosarcoma:
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The tumour is
composed of interlacing fascicles of spindle cells with eosinophilic
cytoplasm and blunt ended nuclei (cigar shaped)
The appearance of the tumour varies according to the degree of
differentiation.
Dermal leiomyosarcoma demonstrates an irregular outline. The tumour cells
blend into surrounding collagenous stroma. A superficial grenz zone may be
present. The tumour is usually located in the dermis but may extend into
the subcutis. The overlying epidermis shows some flattening of the rete
ridges.
Subcutaneous leiomyosarcoma may extend into the lower dermis. A prominent
vascular pattern is evident.
Criteria for
malignancy-
High cellularity , nuclear pleomorphism , atleast one mitotic figure per
10 high power field in cellular areas presence of tumour giant cells and
foci of necrosis.
Small areas of higher mitotic activity known as 'mitotic hot spots' may be
present.
Presence of vascular invasion is indicative of poor prognosis.
VARIANTS:
Leiomyosarcoma
with osteoclast giant cells-
Pleomorphic
leiomyosarcoma-
There is marked pleomorphism with 'MFH' - like areas , extensive
hyalinization and numerous osteoclastic giant cells.
Inflammatory
leiomyosarcoma-
There are small lymphoid aggregates. These tumours are known to have
better prognosis.
Granular cell
leiomyosarcoma-
Intracytoplasmic
eosinophilic granules are present.
Epithelioid
leiomyosarcoma-
There are epitheliod
cells These may be mistaken for melanoma.
Desmoplastic
leiomyosarcoma-
Stromal sclerosis is present.
Myxoid
leiomyosarcoma-
Rarely occur in deep soft tissue. Grossly may be gelatinous in
appearance. Microscopically characterized by extensive myxoid areas.The
spindle cells are separated by pools of hyaluronic acid . In areas tumour
cells are arranged in cord- like pattern reminiscent of myxoid
chondrosarcoma. Mitotic rate is low. The tumour is not as aggressive as
previously suggested. Immunohistochemistry may be necessary for
distinction from a nerve sheath tumour.
HISTOCHEMISTRY:
Well differentiated cells demonstrate myofibrils with Masson Trichrome
stain as deep red longitudinal parallel lines. PAS positive
intracytoplasmic glycogen is present . Reticulin stain show a fine
reticulin network between muscle fibres.
IMMUNOHISTOCHEMISTRY:
There is
Vimentin and Smooth muscle actin positivity in the cytoplasm.
Desmin is positive (often focal) in 70% cases and is usually absent in
high grade tumours.
Pan-muscle actin (HHF-35) is usually positive.
Cytokeratin and S100 protein positivity is noted in 30 - 40% cases.
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