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Soft Tissue Tumors Part 3
Muscle, Vascular, Nerve, Other
Leiomyosarcoma-general
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Revised: 13 July 2010, last major update - August 2009
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
Leiomyosarcoma: general, cutaneous, epithelioid, myxoid, pleomorphic, rhabdoid features
Definition
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● Smooth muscle tumor with atypia plus either mitotic activity, tumor cell necrosis or size > 10 cm
● 10% of adult soft tissue sarcomas
● Variants are described separately above
Epidemiology
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● Skin/subcutis: see cutaneous variants above; better survival than retroperitoneal tumors
● Retroperitoneum: third most common retroperitoneal sarcoma after liposarcoma and MFH; usually women, 5 year survival is only 29%
● Immunocompromised patients: associated with EBV in HIV patients; may be multifocal
Sites
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● Usually extremities
● Often arises from large vessels (AJSP 2002;26:14), most commonly inferior vena cava, saphenous vein, femoral vein, pulmonary artery, femoral artery
● Also occurs in retroperitoneum, superficial or deep soft tissues
Case reports
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● 26 year old man with EBV+ tumor after heart transplantation (AJSP 2000;24:614)
● 54 year old man with tumor of inferior vena cava (Archives 2003;127:e423)
● 69 year old man with tumor of internal jugular vein (World J Surg Oncol 2008;6:113)
Treatment and prognosis
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● Excision with clear margins (enucleation is inadequate treatment)
● Often recurs locally or metastasizes
● Lung is common site of metastasis, lymph nodes are uncommon site
● Poor prognostic factors: retroperitoneal, mesenteric or other deep location, size > 5 cm, age > 62 years, high grade, tumor disruption by prior incisional biopsy or incomplete excision (Cancer 2007;109:282), possibly nuclear c-myc expression (Mod Pathol 2009 Jul 24 [Epub ahead of print])
● In extremities, poor prognostic factors are large size and high mitotic rate; best treatment is wide surgical excision plus adjuvant radiation therapy (Eur J Surg Oncol 2004;30:565)
Clinical images
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12 cm tibial tumor
Gross description
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● Large, soft, often necrosis, hemorrhage and cystic degeneration
● May project into lumen of major vessels or be intramural
Gross images
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Recurrent tumor Fusiform tumor of arm Tumor of popliteal vein
with cystic cavity
Images: leg tumor #1; #2; retroperitoneal tumor; thigh tumor; necrotic tumor within skeletal muscle
Micro description
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● Fascicular growth pattern (bundles intersect at right angles)
● Tumor cells merge with blood vessel walls
● Palisading of spindle cells with eosinophilic fibrillary cytoplasm, focal granularity
● Nuclei are cigar-shaped and blunt-ended with variable atypia, often with cytoplasmic vacuoles at both ends of nuclei (unlike neural lesions)
● Mitotic figures are common
● May have hemangiopericytoma-like vasculature, nuclear palisading, myxoid change, osteoclast-like giant cells
●
Often infiltrates into adjacent tissue
● See also variants above
Malignant criteria by site
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● Soft tissue: 1-2 MF/10 HPF and deep
● Skin/subcutaneous: 2 MF/10 HPF is definitive, 1 MF/10 HPF if consistent in all fields
● Retroperitoneum: 5 MF/10 HPF is definitive, or 1-4 MF/10 HPF plus necrosis plus size > 7.5 cm
● Vascular: 1-4 MF/10 HPF plus large size plus necrosis
● Diagnosis as tumor of uncertain malignant potential (UMP) if mitotic figures are fewer than above or focal
Micro images
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Malignant based on Pleomorphism and smooth
low power pleomorphism muscle differentiation are evident
Markedly pleomorphic, little evidence Multinucleated giant cells
of smooth muscle differentiation
Tumor of inferior vena cava - cytology, Intravenous tumor
H&E and smooth muscle actin
H&E and h-caldesmon
Retroperitoneum: smooth muscle morphology Marked pleomorphism
and no identifiable smooth muscle
Uncertain malignant potential: 8 cm retroperitoneal tumor with bland cells and < 1 MF/10 HPF
Tumor cells are intimately associated with vessels: Hemangiopericytoma-like
H&E and smooth muscle actin growth pattern
Hereditary retinoblastoma patients: Coagulative tumor MIB index is 35-40%
cell necrosis
Cytology description
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● Fascicles with an mixture of dispersed cells or stripped nuclei
● Most cells are spindled with elongated, blunt-ended, segmented or fusiform nuclei or round/polygonal with round or indented nuclei
● Also pleomorphic cells, occasionally intranuclear vacuoles, mitoses and osteoclast-like giant cells (Diagn Cytopathol 2006;34:597)
Positive stains
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● HHF-35 (90%), alpha-smooth muscle actin (90%), vimentin, desmin (75%) (Cancer 2009 Jul 22 [Epub ahead of print])
● H-caldesmon (Am J Clin Pathol 2000;113:663)
● PTAH (stains myofibrils), keratin (30%), ER (usually in uterine and female retroperitoneal tumors), S100 (occasionally weak staining), EMA (may be focal)
Negative stains
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● CD117
Electron microscopy
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● Some smooth muscle features, including cytoplasmic filaments with focal densities (also present in myofibroblasts), pinocytotic vesicles, thick basal lamina
Molecular / cytogenetics
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● Often complex karyotypes with no consistent aberrations
Differential Diagnoses
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● Leiomyoma - no/rare mitotic activity, no/minimal atypia, small size, no hemorrhage, no necrosis
● Dedifferentiated liposarcoma - usually trunk, better prognosis, well differentiated component present, MDM2 and CDK4 amplification (AJSP 2007;31:1557)
End of Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other > Leiomyosarcoma
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