Table of Contents
Definition / general | Epidemiology | Sites | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Shankar V. Leiomyosarcoma-general. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueleiomyosarcoma.html. Accessed August 14th, 2022.
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
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
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
Contributed by Mark R. Wick, M.D.
Images hosted on other servers:
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
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