Small bowel (small intestine)
Other malignancies
Gastrointestinal stromal tumor (GIST)

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 27 February 2018, last major update August 2012

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

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

Cite this page: Gulwani, H. Gastrointestinal stromal tumor (GIST). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/smallbowelGIST.html. Accessed October 19th, 2018.
Definition / general
  • Tumor which differentiates along line of interstitial cells of Cajal, the gut's pacemaker cell

Duodenum:
  • Median age 56 years (range 10 - 88 years)
  • Associated with neurofibromatosis type 1 (often with multiple tumors)
  • Often long period to recurrence or metastases
Sites
  • 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)

Duodenum:
  • 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
Treatment
  • 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

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

Images hosted on PathOut server:

Case of the Week #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

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

Images hosted on PathOut server:

Case of the Week #237:



Case of the Week #270:

CD34

CD117

CD38

AE1 / AE3

S100

Vimentin



Images hosted on other servers:

Various images (H&E)

Low power jejunal GIST

Various immunostains

Positive stains

Duodenum:
Negative stains

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

Duodenum:
  • KIT mutations in exon 11 (30%) and exon 9 (13%) are common
Differential diagnosis