Colon tumor
Mesenchymal tumors

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

Revised: 3 April 2017, last major update March 2017

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

PubMed search: colonic leiomyosarcoma

Cite this page: Leiomyosarcoma. website. Accessed October 16th, 2018.
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

Images hosted on PathOut server:

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

Leiomyosarcoma with
osteoclast-like giant cells

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