GIST gastrointestinal stromal tumors represent 0.2% of all neoplasms and 80% of gastrointestinal sarcomas. Initially, it was believed that they originated from the Cajal interstitial cells found in Auerbach's neural grid and called the pacemaker of the gastrointestinal tract. But new data show that they are derived from pluripotent stem cells.
Patients with GIST are usually over 50 years of age but may appear in younger individuals and are slightly more common in men. They grow throughout the gastrointestinal tract, 60% are found in the stomach, 30% in the small intestine, 5% in the large intestine, and the remaining 5% in other sites like rectum, esophagus, mesenteric and retroperitoneal.
Most GISTs are sporadic, non-hereditary, and have no clear cause. In rare cases, they have been found in many members of the same family because they have inherited a gene mutation that can lead to GIST. Such syndromes are Familiar Gastrointestinal Stromal Tumor, Neurofibromatosis type 1 and Carney-Stratakis Syndrome.
They are usually asymptomatic tumors that are found accidentally during endoscopic or laparoscopic testing. Depending on their localization and their nature (cytotoxicity, rich blood flow), they may develop with bleeding symptoms (haematemesis, stools, anemia) or with occlusion.
They usually appear as single and rare as multiple lesions and can grow either end-to-side or out-of-the-way into adjacent structures. They are mainly haematogenous mainly in the liver and rarely in the lymph nodes. A particular form of metastases is intra-abdominal disposition that involves a high risk of recurrence or metastases throughout the peritoneal cavity.
Diagnosis is based on CT and MRI. PET (positron emission tomography) is never necessary for staging and monitoring treatment. Endoscopy (gastroscopy, colonoscopy) is performed to diagnose tumors in the upper and lower digestive tract and can be supplemented by endoscopic ultrasound and possibly biopsy.
Histologically we distinguish two types, the spindles representing 70% and the epitheliomas representing 20%. The remaining 10% corresponds to the mixed type where we see both spindle and epithelial elements.
The majority of GIST has activated mutations in the c-kit gene. The mutation produces a ligand that causes uncontrolled activation of tyrosine kinase which in turn causes uncontrolled cell growth. At about 5% there is a mutation in the PDGFR-a gene. A mutation in these genes predicts response to treatment with a tyrosine kinase inhibitor (imatinib, Glivec).
Ro surgical resection with sometimes en block resection of adjacent organs is the treatment of choice and should be pursued in the first operation by avoiding the breakdown of the tumor pseudo-tumor leading to dispersal and implantation. Postoperatively, the patient is treated with iambam (Glivec). The major primary GIST should be enrolled in neoadjuvant chemotherapy with iamabi and in the second year to follow surgery. Also for the treatment of metastasis, the choice of treatment is chemotherapy with a tyrosine kinase inhibitor. Generally laparoscopic resection of GIST is indicated and has no difference in patient survival in the various studies.
Recently, sunitis (Sutend) has been added to GIST in addition to imatinib (Glivec) and three other drugs, nilitinib (Tasigna), everolimus and AMG 707, are under clinical trials