GISTs are defined as mesenchymal tumors arising from the gastrointestinal wall, mesentery, omentum or retroperitoneum. GISTs can be located anywhere in the gastrointestinal tract. The most common sites are stomach (40% to 60%) and small intestine (30% to 40%) [
4]. The mean age of patients with GIST is 53 years. Only about 5% of GIST patients are younger than 30 years [
4]. GISTs of the duodenum make up only 4.5% of all GISTs [
5] and therefore represent a rare tumor entity. Duodenal GISTs are mainly located in the second portion of the duodenum (42 out of 156) and about half of them are malignant [
4]. The woman described in this case report presented with a duodenal GIST as another rare GIST manifestation. On presentation, 41% to 47% of malignant GISTs are metastatic [
6]. These tumors grow expansively without being invasive and sometimes metastasize to the liver or recur locally. A duodenal GIST is usually asymptomatic when small in size and can reach a large size before causing any symptoms. As the tumor enlarges it causes variable symptomatology. The most common presentation is gastrointestinal bleeding which may be chronic and mild or sudden and massive [
6]. Although our patient had a large tumor, she had mild anemia. The next most common presentations are abdominal discomfort, pain and swelling [
7]. Compared to other tumor localizations duodenal GISTs manifest with tumor-associated bleeding in 75% compared to 54% stomach and 28% ileojejunal. In contrast to other localizations duodenal GISTs are thus associated with a dramatically increased risk of upper intestinal bleeding [
8]. Diagnosis can be made with upper gastrointestinal endoscopy [
6]. The tumor is usually exophytic, and appears as a submucosal swelling. Sometimes it presents only as an ulcer, as in our case. The biopsy should be deep, but may not always be diagnostic. Endoscopic ultrasound can help in delineating the submucosal tumor. Alternative diagnostic means include CT, magnetic resonance imaging (MRI), barium study or ultrasonography [
9]. However, CT and MRI seem to be the best imaging modalities for assessment of the primary lesion and detection of metastases [
10]. However, CT scans are not always helpful in specifying the origin of the mass. In several cases reported in the literature, the mass was misdiagnosed as arising from the head of the pancreas [
11]. There is currently uniform agreement that the surgical treatment of choice for GISTs is resection of the tumor with clear surgical margins including adjacent organs as necessary [
10]. As local and regional lymph node involvement is infrequent in GIST, routine lymph node dissection is not advocated [
2,
3,
7,
9] and limited resection is frequently performed. The surgical choice depends not only on the size of the tumor but also on the location in the duodenal wall and the relation to the ampulla of Vater [
10,
12,
13]. Patients with duodenal GISTs close to papilla of Vater should be treated by pancreatoduodenectomy. Various techniques of limited resection for duodenal GISTs have been advocated depending on the site and the size of the tumors. Wedge resection with primary closure can be performed for small lesions if the resulting lumen is adequate and the ampulla can be preserved [
14,
15]. Segmental duodenectomy with side-to-end or end-to-end duodenojejunostomy can be performed for larger tumors located at the third and fourth portion of the duodenum [
14]. Partial duodenectomy with Roux-en-Y duodenojejunostomy can be performed for larger tumors involving the antimesenteric border of the second and third portion of the duodenum [
16]. Although a limited operation procedure, such as wedge or segmental resection, is relatively simple to perform, there is a risk of subsequent anastomotic leakage or stenosis development, as well as later tumor recurrence in patients treated by limited operation. By contrast, pancreatoduodenectomy as a treatment for duodenal GISTs can provide a wider surgical margin but may be associated with excessive morbidity, especially in patients with a tumor of low-grade malignancy [
17]. It is not clear what the optimal surgical margin should be, but a negative one is essential to prevent local recurrence of the tumor. No lymph node dissection is required because they are very unlikely to be involved [
14,
18]. The outcome depends on the pathological features of the tumor and the completeness of surgical resection. Large tumors with high mitotic counts behave much worse than small tumors with low mitotic counts, which are considered benign [
11]. Local recurrence is higher in tumors not completely removed or with a positive microscopic margin. After a review of recent literature the duodenal tumor localization in our case is thus associated with a better prognosis, but with an increased bleeding probability [
8]. These results are in line with the authors' opinion that primary surgery could be the safest therapeutic option for a GIST of this localization. Beside the increased risk of tumor bleeding, caused by the localization, neoadjuvant imatinib therapy would additionally lead to a higher percentage of patients with tumor bleeding. For our patient, there was no indication of adjuvant treatment because the patient presented with severe anemia due to tumor bleeding.