Colon tumor
Mesenchymal tumors
Gastrointestinal stromal tumor (GIST) of colon

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

Revised: 2 November 2016, last major update October 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Gastrointestinal stromal tumor [title] colon

Cite this page: Gastrointestinal stromal tumor (GIST) of colon. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorgist.html. Accessed December 6th, 2016.
Definition / General
  • Tumors that differentiate along lines of interstitial cells of Cajal, the gut's pacemaker cells (Mod Pathol 2003;16:366)
Essential Features
  • Mesenchymal spindle cell neoplasm caused by KIT or PDFRGA mutations
  • Risk stratification is based on location, size and mitotic rate
  • Very rare in colon; rectal GISTs account for roughly 5% of all GISTs
Terminology
Sites
Clinical Features
Prognostic Factors
  • Risk of disease progression for rectal GISTs depends on tumor size and mitotic rate (Semin Diagn Pathol 2006;23:70)
    • If mitotic rate is < 5 per 5 square mm, risk of progression is 0% (< 2 cm), 8.5% (> 2 to < 5 cm) or 57% (> 10 cm) (insufficient data for > 5 to < 10 cm)
    • If mitotic rate is > 5 per 5 square mm, risk of progression is 54% (< 2 cm), 52% (> 2 to < 5 cm) or 71% (> 10 cm) (insufficient data for > 5 to < 10 cm)
  • There is insufficient data for progression estimation in colonic GISTs
Case Reports
Treatment
  • Tyrosine kinase inhibitors, including imatinib mesylate (first line) and sunitinib malate
Clinical Images
Images hosted on other servers:

Colonoscopic appearance

Gross Description
  • Often large, bulky, intramural masses
  • Fish flesh or tannish brown parenchyma with hemorrhage, necrosis and cystic softening
Gross Images
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Gastrointestinal stromal tumor of the left colon (image b)

Outer surface of colorectal GIST

Cut surface of colorectal GIST

Micro Description
  • Mesenchymal tumor usually centered in the muscularis propria
  • Spindle cell GISTs: intersecting fascicles of plump spindled cells with eosinophilic cytoplasm within variably hyalinized or edematous stroma
  • Epithelioid GISTs: rounded epithelioid cells with pseudo compartmental organization
  • Skeinoid fibers (extracellular collagen globules) may be seen
  • Muscle infiltration is common but not predictive of behavior
  • Rarely has osteoclast-like giant cells (Arch Pathol Lab Med 2004;128:440)
Micro Images
Images hosted on PathOut server:

Images courtesy of Raul S. Gonzalez, M.D.:

Rectal GIST: low power

Rectal GIST: intermediate power

Rectal GIST: high power



Images hosted on other servers:

Epithelioid cells and osteoclast-like giant cells

Spindled cells

KIT+

CD34+

PDGFRA+

Positive Stains
Negative Stains
Electron Microscopy Description
  • Processes or cell bodies with intermediate filaments showing solitary focal densities
  • Attachment plaques with incomplete lamina, rare myofilaments and smooth endoplasmic reticulum (Ultrastruct Pathol 2002;26:269)
Molecular / Cytogenetics Description
  • 80% have mutations in KIT, which encodes CD117; exons affected include 11, 9, 13 and 17 (Nat Rev Cancer 2011;11:865)
  • 10% have mutations in PDGFRA; exons affected include 18, 14 and 12; these GISTs are often gastric and epithelioid
  • Both mutations have been identified in small incidental GISTs, affirming their importance
  • Up to 10% have neither mutation and are associated with syndromes such as neurofibromatosis type 1 and Carney's triad
Differential Diagnosis