gastrointestinal stromal tumours gist are the most common mesenchymal tumours of the gastrointestinal tract with an increasing incidence. To review the biology, diagnosis and treatment of gastrointestinal stromal tumours. A pubmed search using the phrases 'gastrointestinal stromal tumor', 'imatinib', 'c kit'. The diagnosis of gist is established by histology supplemented by the immunohistochemical marker cd117, which is positive in 95% of cases. Five year survival for malignant gist ranges between 35% and 65% and depends primarily on tumour size, mitotic index and location. The malignant behaviour of gist is best assessed by invasion of adjacent structures and distant metastases.

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Imatinib, a tyrosine kinase inhibitor, is the primary therapy for unresectable, recurrent or metastatic disease. doi: 10.1186/1477 7819 7 61 gists are a subset of mesenchymal tumors and represent the most common mesenchymal neoplasms of gi tract. However, gist is a recently recognized tumor entity and the literature on these stromal tumors has rapidly expanded. An extensive review of the literature was carried out in both online medical journals and through athens university medical library. An extensive literature search for papers published up to 2009 was performed, using as key words, gist, cajal's cells, treatment, imatinib, kit, review of each study were conducted, and data were abstracted. The clinical presentation of gist is variable but the most usual symptoms include the presence of a mass or bleeding.

However, therapeutic agents, such as imatinib have now been approved for the treatment of advanced gists and others, such as everolimus, rapamycin, heat shock protein 90 and igf are in trial stage demonstrate promising results for the management of gists. The online version of this article doi: 10.1186/1477 7819 7 61 contains supplementary material, which is available to authorized users. Gists gastrointestinal tumors are a subset of mesenchymal tumors and represent the most common mesenchymal neoplasms of gi gastrointestinal tract. Gastrointestinal stromal tumors are kit expressing and kit tyrosine kinase receptor cd117 signaling driven mesenchymal tumors. Many gist tumors have an activating mutation in either kit or pdgfrα platelet derived growth factor receptor alpha 1 .

Their origin was at first attributed to cajal's cells, in mesodermal tissue but it has nowadays been recognized that gists arise from multipotential mesenchymal stem cells 2 . However, gist is a newly recognized tumor entity but the literature on these stromal tumors has swiftly expanded. In the past, these tumors were presumed to have elements of smooth muscle smooth muscle origin , so they were classified as leiomyomas, leiomyosarcomas and leiomyoblastomas 3 . The term was first coined by mazur and clark, in 1983, in order to describe a heterogeneous group of gastrointestinal non epithelial neoplasms. In 1998, hirota reported that gists contained activating c kit mutations, which play a central role in its pathogenesis 4 . Furthermore, gists express cd34 cluster designation 34 and the kit on their surface 5 . Moreover, it was their origin that lead to the introduction of a chemotherapeutic regimen, imatinib mesylate, a tyrosine kinase inhibitor for c kit.

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The incidence of gist is estimated to be approximately 10 20 per million people, per year. However, the precise incidence of gist is unknown because of the incomplete definition and classification 10 . Over 90% of gists occur in adults over 40 years old, in a median age of 63 years. The incidence between the sexes is the same, although a study reported that there is a slight predominance of males 7 . There are no elements that indicate any association with geographic location, ethnicity, race or occupation.

Five to ten percent of gists arise from the colon and rectum, and 5% are located in the esophagus. Other less common locations are those outside of the gi tract, like mesentery, retroperitoneum and omentum. However, there have been reported rare cases in the gallbladder, pancreas, liver and urinary bladder.

In cases, where gist occurs outside the gi tract, the tumors are known as extra gastrointestinal stromal tumors egists 11 . Furthermore, only 70% of the patients are symptomatic, while 20% are asymptomatic and 10% are detected at autopsy 6. The symptoms and signs are not disease specific and as a consequence, about 50% of gists have already metastases at the time of diagnosis. The clinical signs and symptoms are related to the presence of a mass or bleeding 12 .

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However, as it is mentioned above, 10% remain asymptomatic, because of their small size lt 2 cm and they are diagnosed incidentally 13 . Bleeding comprises the most common symptom and it is attributed to the erosion of the gastrointestinal tract lumen. Bleeding occurring into the abdominal cavity leads to acute abdominal pain that usually ends up in emergency surgery.

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Nevertheless, bleeding can take place into the gi tract lumen, causing haematemesis, melena or anemia. However, most of the patients present with vague symptoms, such as nausea, vomiting, abdominal discomfort, weight loss or early satiety. Rapture of gists into the peritoneal cavity is rare and it causes life threatening intraperitoneal hemorrhage 14 . These symptoms include dysphagia in the esophagus, biliary obstruction around the ampula of vater or even intrussusception, in the small bowel. On the other hand, distant metastases most commonly occurs in gist tumors of peritoneum, omentum, mesenteric areas and liver, while in egists tumors are rare. At this point, it is important to mention that rectal gists frequently metastasize to the lung. The intra abdominal lesions result from tumor cell seeding into the abdominal cavity, whereas liver metastases derive probably from haematogenous spread.