The gastrointestinal stromal tumor, or GIST, is a rare tumor of the GI tract can be benign or cancerous. According to the American Cancer Society, in the United States, an estimated 4,500 to 6,000 new cases of GIST are diagnosed each year. A gastrointestinal stromal tumor or GIST develops in the interstitial cells of Cajal which line the walls of the gastrointestinal tract. These specialized cells are referred to as the pacemakers of the GI tract because they initiate and control motility of food and liquids through the GI tract.
These tumors can develop in any portion of the GI tract but 50 to 70 percent start in the stomach, 20 to 30 percent form in the small intestines, while the remaining percentage develop in the esophagus, colon, rectum, and anus. GISTs are most often diagnosed in people over the age of 50. There is a slightly higher incidence of occurrence in males than females and Afro-Americans than in Caucasians.
The exact cause of GISTs is unknown. It is known that people with GISTs have a mutation in the oncogene, c-kit. Oncogenes are genes that promote cell growth and division. Normally, the c-kit gene is inactive and is activated only when there is a need for more interstitial cells of Cajal. In most cases of GIST, the c-kit gene was found to be mutated and always active.
Currently, known risk factors for GISTs are few. In rare cases, several members of a family have been diagnosed with GISTs. This leads to the theory that a mutated gene, PDGFRA, is inherited and responsible for the genetic syndrome of GISTs. People who have type 1 neurofibromatosis have a high risk for GISTs. Type 1 neurofibromatosis is an inherited disease caused by a defect in the gene NF1. These individuals develop benign tumors that form in nerves in the skin and throughout the body.
To establish a diagnosis, a physician obtains the patient’s medical history, performs a physical exam and will order imaging studies, such as a MRI or PET scan. A biopsy or sample of tissue is obtained and examined under a microscopic to confirm the diagnosis.
Treatment depends on the size and location of the tumor and if the GIST is cancerous. Surgery is the standard treatment. In 2002, the FDA approved the use of imatinib, which is a drug that targets the faulty genes responsible for cell growth. It can be used as the only treatment or given before and after surgery. In cases of metastasis, a patient will take imatinib for the rest of her life.