Gastrointestinal Stromal Tumors (GIST)
2
GIST may show wide range of morphology
epithelioid cells (rounded cells)
mixture
Spindle stretched
Smooth muscle differentiation can be seen in these
tumors
very important because we need to
differentiate between GIST and the tumors that are
originally derived from smooth muscle which are
leiomyoma
95% of GISTs are positive for CD117 (c-KIT)
immunostain
to detect the gene
color the antibody with a brown color, this is why the
cells, which express this antigen, will be colored with
brown color, so the cells in brown color have the
CD117 (c-KIT) mutation
The Hematoxylin stain works in an opposite way, it colors the negative cells
(cells which lack the antigen)
Clinical picture:
the mass of tumor may affect the region where it
exists
depends on the size of the tumo
Asymptomatic
might affect the mucosa and lead to mucosal ulceration
Prognosis:
divided into risk categories (low – high) depending on
Tumor size.
Mitotic count per 50 HPF (high power field)
Location (gastric, esophageal or intestinal)
Metastases can appear after 20 years of removal of the original tumor, mainly
to liver.
Treatment:
Surgery
Targeted therapy like imatinib mesylate which is only targeted against
tyrosine kinase. That means they target only the cells that exhibit the mutation