Understanding Gastrointestinal Stromal Tumors (GISTs)

Gastrointestinal stromal tumors, or GISTs, are the most common type of tumors found in the digestive system. They usually develop from special cells called interstitial cells of Cajal or their early forms. Recognizing the features of GISTs is very important for doctors to diagnose and treat them effectively.

Here are the key features that help identify GISTs:

1. Cell Structure:

   • GISTs usually look like round tumors that are often surrounded by a clear boundary.
   • Under a microscope, they often show two main shapes: spindle cells (which look like long, thin cells) and epithelioid cells (which are more rounded). Most GISTs, about 70-80%, are spindle-shaped, while 20-30% are epithelioid.

2. Cell Details:

   • The cells within GISTs often form a pattern that looks like intersecting lines.
   • Their nuclei (the part of the cell that contains DNA) are typically oval or stretched out and don’t divide very often. The substance inside these cells is minimal and has a pinkish color.

3. Identifying Markers:

   • GISTs commonly show a marker called CD117 (also known as c-KIT) in about 95% of cases. This marker is very important for diagnosis.
   • Other markers include CD34, which is found in about 60-70% of cases, and smooth muscle actin (SMA), which can vary between tumors.
   • Some GISTs may not show CD117, especially if there are changes in a gene called PDGFRA.

4. Genetic Changes:

   • Changes in the c-KIT gene happen in about 75-80% of GISTs. Changes in the PDGFRA gene are seen in around 5-10% of cases.
   • These genetic changes help explain how GISTs develop and how they respond to certain treatments.

5. Cell Division Rate:

   • The rate at which cells divide in GISTs can differ. However, if there are fewer than 5 dividing cells in a certain area, the tumor is usually considered low grade. If there are more, it is seen as high grade.

In summary, understanding GISTs involves looking closely at their cell structure, characteristics, special markers, and genetic changes. All these factors are essential for getting the right diagnosis and treatment.