Bone metastases from gastrointestinal stromal tumors (GISTs).

e20527 Background: Liver and peritoneum are the most common site of recurrences from gastrointestinal stromal tumors (GISTs). Bone metastases represent a rare finding in clinical practice and their biological significance and clinical management remain unsettled. Methods: We reviewed all patients with advanced/metastatic GIST at our institution and focused on cases with bone metastases, describing the clinical and radiological features of these lesions. Results: Among 71 patients, four had bone metastases. Two were female (82 and 54 years of age) and two were male (62 and 44 years of age). All four of them had an high-risk primary GIST, localized in small intestine in three cases, and in the stomach in the other one. One patient harboured a KIT esone 11 mutation (T>A 69429(p.V559d), one patient had a WT GIST and in the other patients mutational analysis was not assessable. Bone tumour involvement was present at the time of initial diagnosis in two patients, and occurred during the follow-up period after 7...