Imaging gastrointestinal stromal tumors.

BACKGROUND: Because of the recent reclassification of mesenchymal tumors, which was based on a better understanding of the genetics and immunophenotype of gastrointestinal stromal tumors (GISTs), only a limited number of studies have described the radiologic appearance of GISTs. METHODS: This study reviews the imaging characteristics of GISTs, with an emphasis on differentiating benign and malignant tumors using positron emission tomography (PET), computed tomography (CT), and magnetic resonance imaging (MRI). We reviewed the data from 53 cases of GISTs treated at our institute. The imaging studies from these cases, which were recorded at our institute from January 1998 through June 2003, included PET, CT, and MRI. RESULTS: Of the 53 GIST cases, stomach and small bowel tumors accounted for 80% of the tumors. Malignant lesions were larger and more heterogeneous, had ulcerations, and were PET positive. Peritoneal and liver metastases were most common. CONCLUSIONS: PET, CT, and MRI appear to be useful in differentiating nonmetastasizing from malignant GISTs.