Resected duodenal gastrointestinal stromal tumour with an affected margin and exon 9 mutation: adjuvant therapy

We report on a 44-year-old female patient complaining of epigastric pain with an initial diagnosis of acute pancreatitis. Three months later, the symptoms reappeared and an abdomen computed tomography scan showed a mass in the third portion of the duodenum. After surgical resection, the pathologist confirmed malignant mesenchymal proliferation with a mitotic index of 2 mitoses/50 HPF. There was no tumour necrosis. The proliferation index (Ki 67) was 2%. A mutational analysis was carried out, which identified a mutation in c-KIT exon 9, with duplication of codons 502 and 503. A radical surgery was rejected by the patient and adjuvant therapy with imatinib at an initial dose of 400 mg/day was considered, with the intention of increasing the dose to 800 mg/day because of the presence of mutation in c-KIT exon 9 related to a poor response to imatinib. However, because of the adverse effects, the increase in the dose was ruled out, and the patient completed 1 year of adjuvant therapy with no evidence of disease relapse.