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Small Bowel Gastrointestinal Stromal Tumors: Imaging and Clinical Correlates

Small Bowel Gastrointestinal Stromal Tumors: Imaging and Clinical Correlates

Franco Verde MD



  • FV: None
  • HR: Royalties, Myriad Genetics, Inc
  • EF: Research support, Siemens AG Advisory Board, Siemens AG Research support, GE Company Advisory Board, HipGraphics, Inc co-founder


Outline of Presentation

  • Introduction
    • Epidemiology
    • Presentation
  • Pathology
    • Terminology
    • Assessment
    • Staging
  • Imaging Appearance
    • CT protocol
    • Location
    • Size
    • Enhancement
    • Additional Features
    • Metastatic Disease
    • Additional cases per site
  • Treatment
  • Prognosis


Introduction: Epidemiology

  • Primary small bowel (SB) tumors are rare
    • 9410 new cases, 1260 deaths (0.2% of all cancer deaths)
  • Gastrointestinal stromal tumors (GISTs) comprise 8-15% of all SB tumors
  • Small bowel GISTs (SB-GISTs) are frequently
    • Older (mean age 60.6 years)
    • Caucasian (79%)
    • Male (55%)


Introduction: Presentation

  • Patients may present with
    • Abdominal pain
    • Bleeding
    • Obstruction
    • Palpable abdominal mass
  • SB-GISTs may also be incidental
    • Frequently when lesion is less than 2 cm
    • When resecting bowel for a different reason (i.e. Whipple procedure for pancreatic adenocarcinoma with tiny incidental duodenal GIST)


Histopathology: History

  • SB-GISTs were previously described as GI leiomyomas, leiomyoblastomas, leiomyosarcomas or neurofibromas or schwannomas
  • Mazar and Clark first used the term gastric stromal tumor in 1983 to describe non-epithelial gastric masses that lacked features of schwann cells or smooth muscle


Pathology: Terminology

  • Originate from common precursor of interstitial cells of Cajal
    • Named after 19th century Spanish neuroanatomist
    • Intermediates between GI autonomic nervous system and smooth muscle cells
    • Found throughout the GI tract around the myenteric plexus in the muscularis propria
    • Kit and Kit-ligand (stem cell factor) positive and dependent cells
      • Kit or Kit-ligand deficient mice lack Cajal cells and have intestinal dysmotility


Pathology: Gross

  • 5 main gross pathologic patterns of SB-GISTs
    • sessile intraluminal small polyps
    • tumors with a small intraluminal and a larger extra-luminal component
    • pedunculated extra-luminal mass
    • extra-luminal mass only
    • large extra-luminal masses with cavitation, hemorrhage, necrosis and luminal communication.
  • Usually pink-tan and occasionally gray-white or yellowish


Pathology: Immunohistology

  • GISTs are predominately related to gain-of-function mutations of KIT gene
    • Which encodes for tyrosine kinase transmembrane receptor
    • 85% of all GISTs have some variable mutation of the KIT gene: typically exons 9, 11, 13, or 17
    • Each exon codes for a different component of the tyrosine receptor
    • Receptor responsible for initiating a signaling cascade involved in cellular survival, growth, and differentiation
  • Up to 10% of GISTs without detectable KIT gene mutation will have a PDGRFA gene, another tyrosine kinase cell surface receptor.
  • Rarely, no KIT or PDGRFA gene mutation is found. Mutations have been found in other downstream genes (e.g. BRAF, NF1, or RAS)


Pathology: Assessment

Modern pathologic assessment of GISTs include the following parameters
  • Location
  • Size
  • Subtype
  • # of mitoses per 50 high powered fields (HPFs)
  • Presence of necrosis
  • Presence of lymphatic and venous invasion
  • Surgical margin assessment
  • Node assessment
  • Presence of metastatic disease
  • Immunostains
  • Preoperative treatment


Pathology: Assessment

  • Location
    • Gastric, small bowel, etc.
    • Small bowel GISTs have been shown to have a higher rate of progressive disease compared to gastric origin
    • Duodenal GISTs are more common than jejunal or ileal GISTs
  • Size
    • Main determinant in prognosis and TNM classification
    • Categorized into
      • T1: < 2 cm
      • T2: > 2 cm and < 5 cm
      • T3: > 5 cm and < 10 cm
      • T4: > 10 cm


Pathology: Assessment

  • Subtype
    • Spindle cell morphology is most common
    • Small percentage epithelioid
    • Rarely mixed pattern
  • Mitotic Rate
    • Next most important determinant of risk of progressive disease
    • G1 or low-grade: less than 5 mitoses per 50 HPFs
    • G2 or high-grade: more than 5 mitoses per 50 HPFs
  • Necrosis
    • Either coagulative or liquefactive
    • Presence of necrosis is not a determinant of progression
  • Lymphatic or venous invasion
    • Described but not used in staging


Pathology: Assessment

  • Nodal disease
    • Rarely does GIST metastasize to regional nodes
  • Metastatic disease
    • Found as peritoneal implants or hepatic disease
  • Immunostains
    • Positive and routinely tested for evaluating a small bowel tumor:
      • C-kit
      • DOG-1 (cell-surface novel marker, not usually found in other soft tissue tumors)
      • PDGFRA (tested when C-kit is negative)
    • Negative and routinely tested for:
      • Desmin and SMA – smooth muscle markers found in leiomyomas
    • S100, HMB45, cytokeratin – found in tumors of epidermal origin (e.g. schwannoma or melanoma)
  • Preoperative treatment: if a tyrosine receptor blocker was used (i.e. imatinib mesylate)


Pathology: AJCC Staging

Pathology:AJCC Staging


Imaging: Protocol Optimization

Recommended 64 MDCT protocol
  • Arterial (bolus triggered) and venous phases (60 second delay) at 4-5 mL/s
  • 120 kVp
  • 250 mAs
  • 0.8 pitch
  • 64 x 0.6 mm collimation
  • 0.75 mm axial and 3 mm axial, sagittal, and coronal reconstructions
  • 1000 mL water PO


Imaging: Location

  • Typically appear as extra-luminal masses with a small intra-luminal component (tip-of-iceberg)
  • Duodenum more common than jejunum or ileum
  • Example of a low grade, 1.9 cm, spindle type GIST arising from the duodenum with tiny intraluminal component (arrow)


Imaging: Location

  • Duodenal GISTs can mimic neuroendocrine tumors given seemingly completely extraluminal appearance
  • Example of a 3.6 cm a low grade, spindle type, GIST arising from the duodenum.
    • Mass was resected with pre-operative diagnosis of neuroendocrine tumor


Imaging: Location

  • Some very large SB GISTs may have no apparent source and seemingly arise from the mesentery and mimic other sarcomas
  • Example of 33 cm high grade jejunal GIST with 50% necrosis with extensive local mass effect


Imaging: Size

  • SB GISTs demonstrate a spectrum of sizes typically 5 to 10 cm with approximate similar percentages of less than 5 cm or greater than 10 cm
  • Example of a 5 cm low grade jejunal GIST


Imaging: Enhancement

  • Noncontrast demonstrates homogenous soft tissue density (lower arrow)
  • Focal calcifications can be seen (upper arrow)
  • Example of a 6.5 cm high grade, necrotic, GIST arising from distal jejunum.


Imaging: Enhancement

  • Enhancement pattern is variable depending on size, phase of contrast, and presence of necrosis or luminal connection
  • Example of a 2.5 cm duodenal GIST with heterogeneous enhancement on arterial (A) phase becoming homogenous on venous (B) phase. Note degree of enhancement is similar to renal cortex


Imaging: Enhancement

  • If the GIST is large, necrosis will likely be present and appear and central hypoattenuation and a rim of enhancing viable tissue.
    • Example of a high grade duodenal GIST with extensive necrosis.
  • Central heterogeneous enhancement in smaller GISTs (lower image) does not necessarily indicate necrosis.
    • Example of a low grade duodenal GIST without necrosis.


Imaging: Additional Features

  • Intratumoral air and fluid levels or debris can be seen when there is luminal communication
  • Example of low grade GIST arising from the duodenum with extensive necrosis.
    • Note luminal communication demonstrated by intratumoral air (arrow)
Imaging:Additional Features


Imaging: Metastatic Disease

  • Metastatic disease is usually seen as mesenteric or liver lesions
  • Mesenteric nodules are usually small, round and may enhance.
  • Liver metastases are hypovascular, round, and well demarcated.
Imaging:Metastatic Disease


Imaging Additional Cases - Duodenum

ImagingAdditional Cases - Duodenum


Imaging Additional Cases - Jejunum

ImagingAdditional Cases - Jejunum


Imaging: Additional Cases - Ileum

Imaging:Additional Cases - Ileum



  • Surgical resection is mainstay therapy for isolated small tumors without evidence of metastatic disease.
  • Laparoscopic resection may be attempted for small tumors with open procedures reserved for larger tumors.
  • Imatinib mesylate, a tyrosine kinase inhibitor, is first line therapy for patients who are poor surgical candidates, or show evidence of recurrence or metastatic disease.
    • Can also be used as neoadjuvant therapy to preoperatively shrink large tumors


Imaging Surveillance

  • Surveillance after surgery includes CT scanning with contrast every 3 to 6 months.
  • Low grade small tumor may have scans every 6 to 12 months.
  • Patients receiving imatinib mesylate therapy may have scans every 3 months.
  • Dual phase imaging is recommended as arterial phase may detect new enhancing components in stable disease that may wash out during venous phase and be overlooked.


Prognosis: Size and Mitotic Rate Dependent

PrognosisSize and Mitotic Rate Dependent



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  • Franco Verde MD
  • Ralph Hruban MD
  • Elliot K. Fishman MD

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