Colon tumor
Mesenchymal tumors

Author: Raul S. Gonzalez, M.D. (see Authors page)

Revised: 28 February 2017, last major update February 2017

Copyright: (c) 2003-2017,, Inc.

PubMed Search: Leiomyoma [title] colon

Cite this page: Leiomyoma. website. Accessed April 23rd, 2017.
Definition / General
  • Benign smooth muscle proliferation of colon
Essential Features
  • Benign incidental tumor arising in muscularis mucosae
  • "Symplastic leiomyoma" refers to benign tumor with bizarre nuclear atypia and possibly increased mitotic activity
  • Most gastrointestinal tract leiomyomas arise in colon
  • Majority arise in rectosigmoid (Mod Pathol 2001;14:950)
Clinical Features
  • Benign
  • More common in men
  • Median age is 62 years
  • Generally discovered incidentally during colonoscopy
Case Reports
  • Total excision is adequate treatment
Clinical Images
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Leiomyoma on colonoscopy

Endoscopic removal of a leiomyoma

Gross Description
  • Firm, white, well delineated nodule or polyp, generally < 1 cm
Micro Description
  • Well differentiated smooth muscle cells with red fibrillar cytoplasm, arranged in fascicles and arising from muscularis mucosae (Arch Pathol Lab Med 2011;135:1311)
  • Usually no mitotic activity or necrosis
  • Symplastic leiomyomas demonstrate significant atypia and possibly increased mitotic activity
Micro Images

Images hosted on PathOut server

Contributed by Dr. Raul Gonzalez, University of Rochester Medical Center (USA):


Symplastic leiomyoma

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Leiomyoma of muscularis mucosa

Symplastic leiomyoma

Positive Stains
Negative Stains
Differential Diagnosis