Soft tissue

Smooth muscle

Leiomyosarcoma

Leiomyosarcoma-general

Author: Vijay Shankar, M.D.

Topic Completed: 1 November 2012

Minor changes: 25 May 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Leiomyosarcoma [title] soft tissue

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Table of Contents

Cite this page: Shankar V. Leiomyosarcoma-general. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueleiomyosarcoma.html. Accessed September 20th, 2021.

Definition / general

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

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% (Stanford University)
Immunocompromised patients: associated with EBV in HIV patients; may be multifocal

Sites

Usually extremities
Often arises from large vessels (Am J Surg Pathol 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, rarely in bone, breast, colon, epididymis, mediastinum

Malignant criteria by site:

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
Diagnose as tumor of uncertain malignant potential (UMP) if mitotic figures are fewer than above or focal

Case reports

8 year old girl with oral cavity tumor (J Cancer Res Ther 2012;8:282)
26 year old man with EBV+ tumor after heart transplantation (Am J Surg Pathol 2000;24:614)
54 year old man with tumor of inferior vena cava (Arch Pathol Lab Med 2003;127:e423)
58 year old man with mediastinal tumor (Korean J Thorac Cardiovasc Surg 2012;45:192)
69 year old man with tumor of internal jugular vein (World J Surg Oncol 2008;6:113)
70 year old man with 25 cm epididymis mass (Case Rep Urol 2012;2012:236320)

Treatment

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;22:1432)
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

Images hosted on other servers:

12 cm tibial tumor

Oral cavity tumor

Epididymis mass (25 cm)

Internal jugular vein

Gross description

Low grade tumors are hard masses and resemble leiomyomas, with white whorled cut surface
High grade tumors are large, soft, often with necrosis, hemorrhage and cystic degeneration
May project into lumen of major vessels or be intramural

Gross images

Images hosted on other servers:

Leg tumor

Retroperitoneal tumor

Thigh tumor

Bone

Microscopic (histologic) description

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, some may show extensive pleomorphism mimicking MFH
Often infiltrates into adjacent tissue
See also variants above

Microscopic (histologic) images

AFIP images

Retroperitoneum smooth muscle morphology

Marked pleomorphism, no identifiable smooth muscle

Uncertain malignant potential: 8 cm retroperitoneal tumor with bland cells and < 1 MF / 10 HPF

Malignant based on low power pleomorphism

Pleomorphism and smooth muscle differentiation evident

Markedly pleomorphic, little evidence of smooth muscle differentiation

Multinucleated giant cells

Contributed by Mark R. Wick, M.D.

Deep soft tissue

Storiform growth

Retroperitoneal

Images hosted on other servers:

Spindle cells arranged in interlacing bundles

Mitotic figures

Masson trichrome

Desmin+

SMA+

Thigh, moderate nuclear pleomorphism

Pronounced nuclear pleomorphism

Foci of coagulative tumour cell

MIB1

Epididymis tumor

Intravenous tumor

Tibial tumor

Mediastinal tumor

Cytology description

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

HHF35 (90%), alpha-smooth muscle actin (90%), vimentin, desmin (75%, Cancer 2009;115:4186)
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), occasionally CD34

Negative stains

CD117

Electron microscopy description

Some smooth muscle features, including cytoplasmic filaments with focal densities (also present in myofibroblasts), pinocytotic vesicles, thick basal lamina

Molecular / cytogenetics description

Often complex karyotypes with no consistent aberrations

Differential diagnosis

Dedifferentiated liposarcoma: usually trunk, better prognosis, well differentiated component present, MDM2 and CDK4 amplification (Am J Surg Pathol 2007;31:1557)
Leiomyoma: no/rare mitotic activity, no/minimal atypia, small size, no hemorrhage, no necrosis