Expression of c-KIT oncoprotein in gastrointestinal stromal tumors in adults and children: guideline for diagnosis and treatment.

Gastrointestinal stromal tumors (GISTs) represent a distinct oncogenetic entity that is now center stage in clinical trials of kinase-targeted therapies. These neoplasms express the c-KIT oncoprotein and occur predominantly in adults, more rarely in children. Two selected cases of GIST expressing c-KIT, including one adult patient and a 9-year-old boy are presented. The adult patient was admitted for palpable abdominal mass without other clinical symptoms. On biopsies obtained by scanner-guided procedure, diagnosis of ganglioneurinoma was proposed with the remark that GIST tumor could not be categorically excluded. At surgery, voluminous encapsulated tumor located at the jejunal wall was found and totally excised. The second patient presented with acute upper gastrointestinal hemorrhage associated with several months history of general fatigue and loss of appetite. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a tumoral mass arising from the lesser curvature of the stomach compatible with GIST. Two small metastatic lesions in the liver were also detected. Combined treatment by surgery and systemic therapy by the tyrosine kinase inhibitor imatinib mesylate was applied.