Imaging features of bone metastases in patients with gastrointestinal stromal tumors.

PURPOSE To determine the prevalence and imaging features of bone metastases in patients with gastrointestinal stromal tumors (GISTs). MATERIALS AND METHODS The medical records of 190 patients with pathologically proven GISTs were reviewed, and patients with bone metastases were identified. Computed tomography (CT) scans of the chest, abdomen, and pelvis were examined for features of bone metastases, and findings were correlated with the results of positron-emission tomography (PET) and histopathology. RESULTS Of 190 GIST patients, six (3.2%) had bone metastases: four patients had multiple bone metastases, and two patients had a solitary metastasis. The maximum diameter of the metastases ranged from 2 to 40 mm, and they most commonly involved the vertebrae, ribs, pelvic bones, and femurs. All lesions were well-marginated and lytic. A soft tissue component was identified in three patients. The bone metastases showed intense fluorine-18 fluorodeoxyglucose (FDG) uptake. After treatment with imatinib mesylate in three patients, the bone metastases developed peripheral sclerosis on CT and became less FDG-avid on PET. All six primary tumors were morphologically high-grade with high mitotic rates and necrosis. CONCLUSION Bone metastases from GISTs are uncommon; when detected with CT, they are characterized by single or multiple lytic lesions with or without soft tissue involvement. A sclerotic rim may appear around the metastatic lesions in response to treatment. Similar to the disease in other sites, bone metastases show intense FDG uptake, which decreases following treatment.