GIST presentation

1. GASTROINTESTINAL
STROMAL TUMORS
DR. PRAMESH PRASAD SHRESTHA
FCPS RESIDENT
DEPARTMENT OF GI SURGERY AND DIGESTIVE DISEASES

2. Introduction
• First described in 1983 by Mazur and Clark
• Before the late 1990s, many non epithelial tumors of thr GI tract were
called GIST
• Hirota et.al(1998):Mutation in KIT
• Most arise from the interstitial cell of Cajal
Demetri, G., chapter author; DeVita, L; Lawrence, TS; Rosenberg, SA., editors (2011). "Chapter 87". DeVita, Hellman, and Rosenberg's Cancer: Principles and Practice of
Oncology (9th ed.). ISBN 978-1-4511-0545-2.

3. • GISTs are the most common mesenchymal tumors of the GI tract.
• Accounts for ~5% of all sarcomas

4. Epidemiology
• Occur in 15-20/One million people, however, true incidence may be
higher.
• Median age: 50-70 years, rare before 40 years
• Pediatric GISTs are considered biologically distinct.
• Similar incidence in males and females.

5. Locations

6. Clinical Features
• Depends largely on the location and size of the tumor
• Small GIST (<2cm): asymptomatic
• Early satiety
• GI bleeding
• Fatigue secondary to anemia
• Pain abdomen
• Abdominal discomfort, distention
• Intestinal obstruction, Large tumors

7. • May present with Acute Abdomen: as a result of tumor rupture,
Intestinal obstruction

8. Pathology
• Most commonly involves muscularis propria
• Ulceration, well circumscribed, Large tumors: Cystic Change
• Cut surface: tan/gray, Fibrous to fleshy
• Believed to arise from Intestitial cells of Cajal, with 95% staining
positive for KIT and 70% for CD34
• Spindle cell type (most common , 70%) or Epitheloid cell type (20%)

9. Associations
• Majority are sporadic
• Carney Traid
• Neurofibromatosis Type 1
• Carney-Stratakis Syndrome

10. Diagnosis
• Clinical, Radiological and Pathological Characteristics
• CECT: imaging modality of choice
• Endoscopic US: small tumors
• MRI
• PET

11. CT scan:
• Appearance vary with size and location
• Soft tissue density with central area of low density
with necrosis (usually in large tumors)
• Tumors are often exophytic
• Peripheral Enhancement, Calcifications are
uncommon
• Metastasis or direct invasion seen
• No Lymph nodes enlargement

12. Biopsy
• Principles:
• EUS-FNA biopsy of primary site is preferred over percutaneous biopsy due to
risk of hemorrhage and intra-abdominal tumor dissemination
• consideration of biopsy should be based on the suspected tumor type and
extent of disease
• Biopsy is necessary to confirm the diagnosis of primary GIST prior to initiation
of preoperative therapy
• Percutaneous image-guided biopsy may be appropriate for confirmation of
metastatic disease
• Testing for Mutations in KIT a PDGFRA is strongly recommended
NCCN Guidelines Version 3.2019 Gastrointestinal Stromal Tumors (GIST)

13. Malignant Potential
• No GIST can be definitively cassified as benign

16. Management
• Choi Response Criteria is used to assess the treatment
• Response of Tumor to Imatinib Therapy:
• Complete Response: Disappearance of all target lesions
• Partial Response:
• >= 10% decrease tumor size in CT scan
• or >= 15% decrease in tumor attenuation in CT
• No new lesions
• Progressive Disease
• >10% increase in sum of Longest diameters of lesions
• Does not meet criteria for partial response
• or increase in size of existing tumor
• Stable Disease: none of the above

17. Surgery
• R0 resection, Histologically negative margins
• Total gastrectomy is rarely indicated (limited intramural extensions)
• Lymph node resection is not required ( low incidence of nodal
metastasis)
• Every effort should be made not to violate the pseudocapsule.
• Resection should be accomplished with minimal mobidity
• Laparoscopic approach may be considered for select GISTs in
favorable anatomic locations
NCCN Guidelines Version 3.2019 Gastrointestinal Stromal Tumors (GIST)

18. Unresectable or Metastatic GIST
• Imatinib
• Surgery may be indicated for:
• Limited progression refractory to imatinib
• locally advanced or previously unresectable tumors after a favorable response
to preoperative imatinib
• management of symptomatic bleeding or obstruction
• Imatinib can be stopped right before surgery and restarted as soon as
the patient is able to tolerate oral medications
NCCN Guidelines Version 3.2019 Gastrointestinal Stromal Tumors (GIST)

23. Differential Diagnosis
• GI Leiomyoma
• GI Leiomyosarcoma
• GI Lymphoma/Gastric Lmyphoma
• GI Schwannoma
• GI Carcinoid