Colon (tumor & nontumor)
Mesenchymal tumors

Topic Completed: 1 March 2017

Minor changes: 31 July 2020

Copyright: 2003-2019,, Inc.

PubMed search: colonic leiomyosarcoma

Raul S. Gonzalez, M.D.
Page views in 2019: 690
Page views in 2020 to date: 617
Cite this page: Gonzalez R. Leiomyosarcoma. website. Accessed August 11th, 2020.
Definition / general
  • Malignant smooth muscle tumor of colon
Essential features
  • Most older reports of colonic "leiomyosarcomas" were probably GIST
  • Small intestine and colon most common GI sites for leiomyosarcoma
Clinical features
Radiology images

Images hosted on other servers:

Ileocecal lesion

Colon wall thickening

Prognostic factors
Gross description
  • Intraluminal, bulging / polypoid mass measuring up to 25 cm
Gross images

Images hosted on other servers:

Leiomyosarcoma (top) vs. GIST (bottom)

Microscopic (histologic) description
  • Resembles leiomyosarcoma at other sites: malignant smooth muscle cells with prominent nuclear atypia, coagulative necrosis and at least 1 mitosis per 10 high power fields
  • Rare examples have osteoclast-like giant cells (Arch Pathol Lab Med 2004;128:440)
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.

Colonic leiomyosarcoma

Nuclear atypia

Numerous mitotic figures

Images hosted on other servers:

Well differentiated tumor

Left: moderately differentiated; right: poorly differentiated

giant cells

Virtual slides
Positive stains
Negative stains
Molecular / cytogenetics description
  • Negative for KIT mutations
Differential diagnosis
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