COMEDK MDS entrance preparations | marker of GIST

Most appropriate marker of GIST- 

A. CD117

B. CD 34 

C. CK

D. Vimentin

Ans. A. CD117 

Gastrointestinal stromal tumor 

1. A gastrointestinal stromal tumor GIST.  is one of the most common mesenchymal tumors of the gastrointestinal tract 1-3% of all gastrointestinal malignancies. . They are typically defined as tumors whose behavior is drrven by mutations in the Kit g or PDGFRA gene, and may or may not stain positively for Kit. 

Signs and symptoms

2. Patients present with dysphagia, GIT hemorrhage or metastases mainly in the liver. . Intestinal obstruction is rare, due to the tumor’s outward pattern of growth. 

3. Generally, the definitive diagnosis is made with a biopsy, which can be obtained endoscopically, 

percutaneously with CT or ultrasound guidance or at the time of surgery. 

4. When GIST is suspected—as opposed to other causes for similar tumors—the pathologist can 

useimmunohistochemistrv specific antibodies that stain the molecule CD 117 also known as c-kit.  

95% of all GISTs are CD 117-positive other possible markers include CD34, desmin, vimentin and 

others. . Other cells that show CD 117 positivity are mast cells. 

If the CD117 stain is negative and suspicion remains that the tumor is a GIST, the newer antibody 

DOG-i Discovered On GIST-i.  can be used. Also sequencing of Kit and PDGFRA can be used to prove 

the diagnosis. 

5. Pathophysiology 

GISTs are tumors of connective tissue, i.e.sarcomas unlike most gastrointestinal tumors, they are 

non-epithelial. 

6. GISTs are thought to arise from interstitial cells of Cajal ICC. , that are normally part of 

the autonomic nervous system of the intestine. They serve a pacemaker function in 

controlling motility. 

7. Most 50-80%.  GISTs arise because of a mutation in a called c-kit. This gene encodes 

a transmembrane receptor for a growth factor termed scf stem cell factor. . The c-kit/CD 117 receptor is 

expressed on ICCs and a large number of other cells, mainly bone marrow cells,mast 

cells, melanocytes and several others. In the gut, however, a mass staining positive for CD117 is likely 

to be a GIST, arising from ICC cells. 

8. The c-kit molecule comprises a long extracellular domain, a transmembrane segment, and an 

intracellular part. Mutations generally occur in the DNA encoding the intracellular part exon 11. , 

which acts as a tyrosine kinase to activate other enzymes. 

9. The tyrosine kinase function of c-kit is vital in the therapy for GISTs. 

10. Therapy Surgery is the mainstay of therapy for non-metastatic GISTs. 

The c-kit tyrosine kinase inhibitor imatinib is used 

CD34 molecule is a cluster of differentiation molecule present on certain cells within the human body. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor.

It may also mediate the attachment of stem cells to bone marrow extracellular matrix or directly to stromal cells.