Anus and perianal area
Benign or nonneoplastic lesions

Topic Completed: 1 September 2014

Revised: 16 January 2019

Copyright: (c) 2002-2019,, Inc.

PubMed Search: Leiomyoma anus
Page views in 2018: 183
Page views in 2019 to date: 36
Cite this page: Weisenberg E. Leiomyoma. website. Accessed February 21st, 2019.
Definition / general
  • Benign smooth muscle tumor
  • Uncommon but most frequent mesenchymal tumor of the anorectum (Odze: Surgical Pathology of the GI Tract, Liver, Biliary Tract and Pancreas, 3rd Edition, 2014)
  • Tumors of muscularis mucosa are not rare but most studies are of anorectum making incidence of true superficial anal tumors difficult to determine
  • Intramural tumors are very rare
  • Secondary involvement of perianal / perirectal tissue by leiomyomas in women is considered more common than true anal intramural leiomyomas
  • Muscularis mucosa of anal transition zone / lower rectum, internal anal sphincter (very rare), anal longitudinal muscle (very rare)
Clinical features
  • Discrete mass
  • May be incidental finding or associated with bleeding
Prognostic factors
  • These are benign lesions
Case reports
  • Local excision, polypectomy, sleeve resection
Gross description
  • Well delineated nodules
  • Superficial lesions are usually under 1 cm
  • Deeper tumors are described as up to 4 cm in size but only rare cases are reported
Microscopic (histologic) description
  • Well delineated nodules composed of bland spindled cells with tapered nuclei
  • Usually paucicellular without atypia but more cellular and atypical cases described
  • Essential absence of mitotic activity
Microscopic (histologic) images

Images hosted on other servers:

Of rectal muscularis mucosa

Positive stains
Negative stains
Additional references