Basics of GIST
Gastrointestinal stromal tumors (GISTs) belong to a group of cancers called soft tissue sarcomas.
Although the exact incidence is still somewhat unclear, it is now estimated that, in the United States, between 3,000 and 5,000 people each year develop GISTs.
There are no known statistics for Latin America.
When GIST tumors are first discovered, the most common symptoms are:
- Vague abdominal discomfort or pain.
- Presence of a palpable abdominal mass.
- Feeling of abdominal fullness.
- Secondary symptoms resulting from tumor bleeding and associated anemia.
A biopsy is usually used to aid in the diagnosis of cancer and GIST. Tissue samples are prepared from the biopsy sample. One method that the pathologist uses to classify tissues is called immunohistochemistry.
Using immunohistochemistry, GIST cells can be summarized as follows1:
- KIT positive-about 95% of the time (the term c-Kit or CD117 may be used instead of KIT).
- CD34 positve-60% to 70% of the time.
- SMA postive-30% to 40% of the time.
- Desmin positive-very rare
- S-100 positive-5%+
Two other stains (tests) that are expressed in almost all GISTs but that may not yet be commercially available include:
- PKC theta (PKCθ)
Both CT scans and PET scans have roles to play in the long-term surveillance of GIST response to imatinib.
Although many factors have been suggested to contribute to malignant potential, the three most commonly quoted factors are size, primary tumor location and mitotic activity.
Other important factors for a high risk of recurrence include:
- Rupture of the tumor either prior to or during surgery.
- Failure to obtain clear margins during surgery.