GISTs - Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GIST) are rare mesenchymal tumors (accounting for 0.1%-3.0% of all gastrointestinal malignancies) which arise from the muscularis propria of the gastrointestinal tract, with development from the interstitial cells of Cajal. Typically they are defined by the expression of c-KIT (CD117, tyrosine growth factor receptor) in the tumor cells. The most frequent site of onset is the stomach, followed by the small bowel, although they can occur in any part of the gastrointestinal tract. The most common sites of distant metastasis are the liver and peritoneum, while metastases to the bone and lymph nodes are less frequent although not impossible. Complete surgical resection is currently the treatment of choice in primary localized disease and it is the only option potentially able to cure the disease. Recently new methods have been introduced in the treatment of GISTs: molecular targeted therapies have shown a significant percentage of response in localized forms and in advanced disease. The study of GISTs, whether primary tumors or advanced disease, can benefit from diagnostic imaging techniques, including contrast-enhanced radiography, ultrasonography with and without contrast enhancement, computed tomography (CT), magnetic resonance (MR) and PET. Alongside these are non-radiologic techniques such as endoscopy and echoendoscopy, which can be useful in the diagnosis of small intramural tumors of the stomach, esophagus and rectum. The aims of the diagnostic techniques are identification, characterization, staging and the evaluation of treatment response.