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Soft tissue tumors

Smooth muscle

Leiomyoma of deep soft tissue


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 23 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Leiomyoma: see also classic, bizarre, cutaneous, epithelioid, genital, retroperitoneal leiomyoma

Definition
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● Very rare tumor of deep subcutis or skeletal muscle of extremities (Stanford University) or retroperitoneum (described below)
● By definition, is distinct from uterus

Epidemiology
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● Tumors of deep somatic soft tissue affect males and females equally (Am J Surg Pathol 2001;25:1134)
● Tumors of retroperitoneum (described below) almost always occur in women
● Can rarely occur in children

Case reports
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● 32 year old man with carpal tunnel syndrome due to atypical deep soft tissue leiomyoma (World J Surg Oncol 2007;5:92)

Treatment and prognosis
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● Excision; rarely recurs

Clinical images
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Hand mass: intraoperative and gross specimen

Gross description
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● Well circumscribed, gray-white
● Usually large at presentation, up to 15 cm
● May have myxoid change

Micro description
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● Fascicles of normal appearing smooth muscle with eosinophilic cytoplasm
● Nuclei are bland and uniform, blunt ended, cigar shaped
● May have dystrophic calcification, degenerative nuclear changes or necrobiotic nodules resembling giant rosettes
● Hyalinization and fatty differentiation can also be seen rarely
● No/minimal atypia
● No/rare mitotic figures (Am J Surg Pathol 1994;18:576); <1 per 50 HPF
● No necrosis

Cytology description
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● Hypocellular smears, with scattered clusters of spindle cells (Diagn Cytopathol 1997;16:326)
● Clustered cells have syncytial appearance
● Bland nuclei have spindled appearance with rounded ends, condensed chromatin
● Usually no necrosis or inflammation
● No mitotic figures

Positive stains
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● Actin, desmin, h-caldesmon
● ER and PR in retroperitoneal tumors

Negative stains
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● S100

Differential diagnosis
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Benign metastasizing leiomyoma: see Am J Surg Pathol 1998;22:897
Myolipoma: prominent fatty change


Retroperitoneal leiomyoma

Definition
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● Well differentiated smooth muscle tumor resembling uterine leiomyoma, with trabecular pattern and hyaline change

Epidemiology
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● Usually occurs in women, mean 45 years (range 25-79 years)
● 40% have history of uterine leiomyoma (J Minim Invasive Gynecol 2008;15:152)
● Rare local recurrence, no metastases (Am J Surg Pathol 2001;25:1355)
● 73% are located in pelvis

Case reports
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● 26 year old woman with pelvic retroperitoneal leiomyoma (Am J Surg 2010;199:e36)
● 42 year old woman with myxoid deep soft tissue leiomyoma with abundant intracellular corpora amylacea (Pathol Res Pract 2007;203:121)
● 42 year old woman with 3 isolated tumors and no uterine tumor (Arch Gynecol Obstet 2009;280:499)
● 46 year old nulligravid woman with lower abdominal and pelvic pain with bloating (J Med Case Rep 2011;5:578)
● 48 year old woman, gravida 2, with incidental pelvic mass and multiple lung nodules (Clin Exp Reprod Med 2011;38:174)
● 49 year old woman with lower extremity mass (Acta Chir Belg 2009;109:112)

Treatment and prognosis
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● Excision; rarely recur locally

Gross images
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Retroperitoneal leiomyoma

Pelvic mass and lung nodules

Micro description
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Leiomyoma:
● 4 cm or less
● Bland smooth muscle tumor
● No mitotic figures
● Very rare at this site

Smooth muscle tumor of uncertain malignant potential:
● Bland smooth muscle tumor
● Either 4 cm or less and 1-4 MF/10 HPF or 5 cm or more and no mitotic figures

Leiomyosarcoma:
● Pleomorphism
● Nuclear atypia or tumor cell necrosis

Micro images
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Classic features of leiomyoma

Retroperitoneal mass

Pelvic mass and lung nodules

Positive stains
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● Smooth muscle actin, desmin
● Trichrome stains smooth muscle red, collagen blue
● ER, PR in women (may arise from hormonally sensitive smooth muscle)

Differential diagnosis
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● GIST tumors: CD117+
Leiomyosarcoma: much more common; necrosis, mitotic figures, pleomorphism
Parasitic leiomyoma: clearly attached to non-retroperitoneal structures

End of Soft tissue tumors > Smooth muscle > Leiomyoma of deep soft tissue


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