Gastrointestinal stromal tumors (GISTs) are rare mesenchymal tumors that arise in the gastrointestinal tract. They range in size from a few millimeters to over 30 cm. Microscopically, GISTs contain eosinophilic structures that stain brightly with PAS. Symptoms are non-specific and include abdominal pain, bleeding, and early satiety. Diagnostic evaluations include CT, EUS, and biopsy. Treatment depends on tumor size and risk of recurrence or metastasis. For resectable disease, surgery is typically recommended, while imatinib is recommended for unresectable, metastatic, or recurrent tumors. Long-term surveillance is important due to the risk of recurrence within the first

1. FACULTY OF MEDICINE
GIST - 2017

3. Made by:
Peter Robiel Mikhail
Peter Atif Ghally

4. GIST
Introduction :
Gastrointestinal stromal tumors (GISTs) are
uncommon mesenchymal tumors that arise
predominantly in the gastrointestinal tract (GIT).

5. EPIDEMIOLOGY
• The most common mesenchymal neoplasms of the GIT. With
an annual incidence of 11-14 per 106.
• They form 0.1%-3.0% of gastrointestinal malignant tumors.
• The median age at diagnosis is 60 years.
• No predilection for either gender but some series suggest a
slight male predominance.
• GIST occurring in the familial form is autosomal dominant.

6. PATHOLOGY
• GIST vary greatly in size from a few millimeters to more than
30 cm, the median size being between 5 and 8 cm.
• Macroscopically, appearance they are smooth gray and white
tumors which are well circumscribed, usually with a
pseudocapsule. A small area of hemorrhage or cystic
degeneration and necrosis may be visible.
• Microscopically, eosinophilic structures, composed of
collagen, which are stained brightly with periodic acid-Schiff
(PAS) stain.

7. Macroscopic pictureMicroscopic picture

8. CLINICAL PRESENTATION
• 70% of the patients with GIST are symptomatic.
• While 20% are asymptomatic and the tumors are detected
incidentally, 10% of the lesions are detected only at autopsy.
• Symptoms and signs are not disease specific ( nausea,
vomiting, abdominal pain and early satiety) , they are related
more to the site of the tumor.
• vague abdominal discomfort (60%-70%).
• Bleeding (30%-40%) due to the erosion into the GIT lumen.
Bleeding occurring into the peritoneal cavity due to a
ruptured GIST can lead to acute abdominal pain presenting as
a surgical emergency. Bleeding into the GI tract lumen,
causing hematemesis, melena or anemia, is usually more
chronic on presentation.

9. • These include dysphagia in the esophagus, biliary obstruction
around the ampulla of Vater or even intussusception of the
small bowel.
• Lymph node metastases are uncommon in GIST.
• Distant metastases most commonly occur in GISTs of the
peritoneum, omentum, mesentery and the liver.

10. INITIAL EVALUATION AND WORKUP
• Contrast enhanced computed tomography (CECT) is the modality of
choice; it is used to characterize the lesion, evaluate its extent, assess the
presence or absence of metastasis at the initial staging workup and for
monitoring response to therapy and performing follow-up surveillance of
recurrence.
• Endoscopic ultrasound (EUS) it assesses the depth of invasion and is useful
in obtaining a tissue sample.
• The efficacy of EUS guided fine needle aspiration (EUS-FNA) has been
pointed out in several studies and the reported accuracy is 80%-85%
• PET is useful in revealing small metastases which would otherwise not
have been picked up on CECT . It helps differentiate an active tumor from
necrotic or inactive scar tissue, malignant from benign tissue and
recurrent tumor from nondescript benign changes.

11. CECT
EUS
PET

12. PRINCIPLES OF BIOPSY AND PATHOLOGICAL
ASSESSMENT
• Routine preoperative biopsy is not mandatory but biopsy is
necessary prior to the initiation of preoperative therapy with
TKI. EUS-FNA biopsy of the primary site is preferred over
percutaneous biopsy as it reduces the risk of tumor
hemorrhage and intra-abdominal tumor dissemination.

13. Management of GIST
Small GIST
• Tumors which are less than 2 cm in the widest dimension are
defined as small GIST. They are usually discovered incidentally
on endoscopy[29]. If these lesions are symptomatic, complete
surgical resection is recommended.
• Small asymptomatic gastric GISTs (less than 2 cm) with no
high-risk EUS features can be managed conservatively with
endoscopic surveillance at 6 to 12 months intervals.

14. LAPAROSCOPY
• Small series and retrospective analyses have shown low
recurrence rates, shorter hospital stay and low morbidity with
a laparoscopic approach. It is mainly used in favorable
anatomic locations like the anterior wall of the stomach,
jejunum and ileum.
IMATINIB MESYLATE
• Patients with advanced GIST started on imatinib have shown a
35%-49% 9 year survival.
NEOADJUVANT IMATINIB – RESECTABLE
DISEASE
• Imatinib is effective in reducing the size of the tumor prior to
resection, increasing the likelihood of negative margins
without significant morbidity.

15. ADJUVANT THERAPY
• Imatinib has been found to be beneficial if continued for 36
months postoperatively, especially in patients with an
intermediate or high risk of recurrence.
UNRESECTABLE, METASTATIC OR RECURRENT
DISEASE
• Imatinib is indicated when primary resection would carry the
risk of severe postoperative functional deficit. It is also
indicated in those who have a widespread metastatic disease
or a recurrence after resection.
RESISTANCE TO IMATINIB:
• Non achievement of stable disease or progression of disease
within 6 months of an initial clinical response is defined as
primary resistance, occurs in 10%-20% patients and relates to
the mutational profile of the tumor.

16. SUNITINIB MALATE
• An orally administered multi-targeted receptor tyrosine kinase inhibitor
which has shown significant and sustained clinical benefit in patients with
imatinib-resistant or imatinib-intolerant GIST.
PERITONEAL AND LIVER METASTASES
• Patients who are medically fit with surgically accessible focally progressive
disease should be considered for resectionto eliminate the drug-resistant
clones that will allow ongoing therapy with imatinib.
• Debulking followed by intraperitoneal chemotherapy with cisplatin and
doxorubicin or mitoxantrone have been attempted; the median time to
recurrence was increased from 8 to 21 months with the addition of
intraperitoneal chemotherapy.
• Surgery in metastatic patients is a case based decision.

17. SURVEILLANCE
• Long term follow up is essential for all
patients, independent of their benign or
malignant characteristics. As the majority of
GISTs tend to recur within the first 3-5 years,
intense follow up is required during this
period.

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