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Bladder

Nonurothelial benign tumors

Leiomyoma


Reviewer: Monika Roychowdhury, M.D., University of Minnesota Medical Center (see Reviewers page)
Revised: 26 April 2011, last major update April 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Benign smooth muscle tumor, similar to counterparts elsewhere
● Defined as sharply circumscribed lesions showing little or no mitotic activity and lacking all but minimal cytologic atypia

Epidemiology
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● Most common benign soft tissue neoplasm of bladder, but < 0.5% of bladder tumors
● Mean age 52-61 years, range 22-78 years, no gender preference

Sites
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● Occur endovesically (63%), intramurally (7%) and extravesically (30%, Urology 2010;76:1425)

Clinical features
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● Usually symptomatic but can be asymptomatic (asymptomatic tumors usually less than 3 cm, Urology 2010;76:1425)
● Endovesical type most frequently produce obstructive or irritative symptoms
● Can be definitively diagnosed on biopsy or TUR without the risk of unsampled leiomyosarcoma (Am J Surg Pathol 2010;34:502); cannot necessarily assess circumscription on TUR specimens, but infiltrative pattern should not be present in a leiomyoma

Prognostic features
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● Lesions with necrosis or mitotic figures, or not well circumscribed, may be well differentiated leiomyosarcoma
● No risk of progression to leiomyosarcoma even if incompletely resected

Case reports
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● Laparoscopic enucleation (J Minim Invasive Gynecol 2009;16:772)

Treatment
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● Excision if symptomatic, enlarging mass or unclear diagnosis

Gross description
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● 0.5 to 4.5 cm, well circumscribed

Micro description
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● Similar histology to leiomyomas elsewhere (large sheets of intersecting smooth muscle fascicles)
● Low cellularity
● May have bizarre or symplastic nuclei, hyalinization, degenerative atypia
● Occasionally has necrosis or myxoid change
● Minimal/no mitotic figures, no atypical mitotic figures (Am J Surg Pathol 2002;26:292)

Micro images
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Strong desmin staining

Various images (see bottom)

Positive stains
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● Actin and desmin (strong)

Molecular
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● Usually diploid

Differential diagnosis
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Uterine leiomyoma (parasitic): Obstet Gynecol 2009;114:611
Well differentiated leiomyosarcoma: not well circumscribed; has necrosis, mitotic figures, abnormal mitotic figures

End of Bladder > Nonurothelial benign tumors > Leiomyoma


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