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Soft Tissue Tumors Part 3
Muscle, Vascular, Nerve, Other
Leiomyoma of deep soft tissue
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Revised: 10 August 2009, last major update - August 2009
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
See also leiomyoma: classic, bizarre, cutaneous, epithelioid, genital
See below - retroperitoneal leiomyoma
Definition
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● Very rare tumor of deep subcutis or skeletal muscle of extremities 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
Treatment and prognosis
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● Excision; rarely recurs
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
● No/minimal atypia
● No/rare mitotic figures (Am J Surg Pathol 1994;18:576)
● 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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● Myolipoma - prominent fatty change
● Benign metastasizing leiomyoma (Am J Surg Pathol 1998;22:897)
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 (AJSP 2001;25:1355)
Case reports
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● 32 year old man with carpal tunnel syndrome due to hand mass (World J Surg Oncol. 2007 Aug 8;5:92)
● 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)
● 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
Clinical images
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Hand mass: intraoperative and gross specimen
Micro description
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Leiomyoma
● 4 cm or less
● Bland smooth muscle tumor
● No mitotic figures
● Considered to be 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
Positive stains
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● Smooth muscle actin, desmin
● Trichrome stains cytoplasm red
● 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 - if clearly attached to non-retroperitoneal structures
End of Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other > Leiomyoma of deep soft tissue
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