Bladder
Nonurothelial benign tumors
Leiomyoma

Author: Monika Roychowdhury, M.D. (see Authors page)

Revised: 8 June 2016, last major update December 2014

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Bladder [title] leiomyoma
Cite this page: Leiomyoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bladderleiomyoma.html. Accessed December 2nd, 2016.
Definition / General
  • 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
  • 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
Clinical Features
  • 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 Factors
  • 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
Treatment
  • Excision if symptomatic, enlarging mass or unclear diagnosis
Gross Description
  • 0.5 to 4.5 cm, well circumscribed
Micro Description
  • 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

Positive Stains
  • Actin and desmin (strong)
Molecular / Cytogenetics Description
  • Usually diploid
Differential Diagnosis
  • Uterine leiomyoma (parasitic): Obstet Gynecol 2009;114:611
  • Well differentiated leiomyosarcoma: not well circumscribed; has necrosis, mitotic figures, abnormal mitotic figures