Small intestine & ampulla
Other malignancies

Topic Completed: 1 August 2012

Minor changes: 7 April 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Gastrointestinal stromal tumor[TI] small bowel[TIAB]

Hanni Gulwani, M.B.B.S.
Page views in 2020: 8,014
Page views in 2021 to date: 3,101
Cite this page: Gulwani H. GIST. website. Accessed May 8th, 2021.
Definition / general
  • Tumor which differentiates along line of interstitial cells of Cajal, the gut's pacemaker cell

  • Median age 56 years (range 10 - 88 years)
  • Associated with neurofibromatosis type 1 (often with multiple tumors)
  • Often long period to recurrence or metastases
  • GI sites: stomach (60%), jejunum and ileum (30%), duodenum (5%) and colorectum (< 5%, Mod Pathol 2003;16:366)
Clinical features
  • Median age 67 years, usually > 50 years
  • May occur in HIV+ children
  • 30 - 50% are malignant with 5 year survival of 50%; malignant tumors metastasize to liver and peritoneum
  • Note: don't call GIST if CD117 negative without expert concurrence
  • Types: spindle cell GIST (70%), epithelioid cell GIST (20%), mixed (10%)
  • CD117- GIST: 5% predilection for stomach or omentum / peritoneum, exhibit epithelioid or mixed type
  • Dedifferentiated GIST: rare, CD117- with marked anaplasia
Prognostic factors
  • Poor prognosis (malignant): over 5 cm, fresh tumor necrosis, extensive hemorrhage unrelated to surgery, hypercellular, marked atypia, 5+ mitotic figures/HPF, smaller cells
  • High risk: > 1 cm and > 5 MF/50 HPF; also infiltrative border within muscularis propria
  • Intermediate risk: 1 - 5 MF/50 HPF and > 1 cm
  • Low risk: < 1 cm (often are serosal)

  • Poor prognostic factors:
    • > 5 cm, > 5 mitoses/50 HPF
    • Epithelioid pattern with mucosal invasion
  • Good prognostic factors:
    • < 2 cm and < 5 mitoses/50 HPF
    • Organoid pattern with low cellularity
Case reports
  • Gleevec (STI571) inhibits tyrosine kinases, including CD117 / KIT and Abl protein in CML
Gross description
  • Often large, well circumscribed, bulky, intramural masses
  • Fish flesh or tan brown appearance, hemorrhage, necrosis, cystic softening

  • Small intramural or external nodules or large masses extending into retroperitoneum
Gross images

Contributed by Riki Turri, P.A. (ASCP)
Missing Image

Small intestine GIST, serosal surface

Missing Image Missing Image

Small intestine GIST, mucosal surface

Missing Image Missing Image

Small intestine GIST, cross section

Case #237

Pelvic mass was attached to the mid jejunum

Microscopic (histologic) description
  • Usually histologically malignant, usually transmural, usually plump spindle cells with eosinophilic cytoplasm within variably hyalinized or edematous stroma
  • Skenoid fibers (extracellular collagen globules) common
  • Muscle infiltration is common but not predictive of behavior
  • May have epithelioid morphology

  • Usually spindle cell tumors, often with skenoid fibers
Microscopic (histologic) images

Contributed by Phoenix D. Bell, M.S., M.D., Jennifer Findeis-Hosey, M.D. and Hanni Gulwani, M.B.B.S.
Missing Image


Missing Image

c-KIT / CD117

Low power jejunal GIST

Case #237

Case #270




AE1 / AE3



Images hosted on other servers:

Various immunostains

Cytology images

Contributed by Phoenix D. Bell, M.S., M.D.
Missing Image

Small intestine GIST, cytology smear

Missing Image

Small intestine GIST, FNA

Positive stains

Negative stains

  • Desmin (trapped smooth muscle fibers are positive)
Electron microscopy description
  • Long interdigitating cytoplasmic processes, intercellular junctions, dense core granules
Molecular / cytogenetics description

  • KIT mutations in exon 11 (30%) and exon 9 (13%) are common
Differential diagnosis
Back to top
Image 01 Image 02