[GIST: Imaging diagnosis, staging, and response assessment]

Diagnosis of gastrointestinal stromal tumors (GIST), which are located in the stomach or colon, is a domain of endoscopy. For midgut GIST is contrast-enhanced multidetector-CT the standard imaging technique. With the development of enteroclysis - MDCT better distension of the small bowel can be achieved to find even small tumors in the bowel wall. For staging of GIST is contrast-enhanced MDCT of the abdomen (and chest) recommended, unless PET/CT is widely available. Contrast-enhanced MRI is used for local staging of rectal tumors and as a problem-solving tool in patients with equivocal lesions at CT of the liver. In chemotherapy-responders, metastases may undergo necrosis and liquefaction with shrinkage. Therefore the RECIST criteria have been found to be unreliable to assess tumor response. The modified CT response criteria of Choi et al. have been developed and validated for more accurate assessment of chemotherapy. If available, is FDG-PET/CT the modality of choice for the follow-up of GIST patients at risk of metastases.