Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract (1,2). They constitute <1% of all gastrointestinal tract malignancies (3). Duodenal GISTs constitute 4.5% of all GISTs (4). GIST of the duodenum is rare than other parts of the small intestine. Around 3300 to 6000 new cases of GISTs are reported per year in the United States (5). Surveillance, Epidemiology and End Result (SEER) data estimated six to eight cases of GISTs per million of the population from 1992 to 2000 (6). In the past, GISTs and leiomyosarcoma were considered as the same entity but now it is revealed that GISTs are CD34 immunoreactive and express tyrosine kinase c-KIT CD117 receptor activity (7).

Gastrointestinal stromal tumors are mesenchymal tumors of the gastrointestinal tract (1). They are located in the submucosa of the gastrointestinal tract (2). Differentials of GIST are leiomyosarcoma of the intestine, dermoid cyst, mesenteric cyst, retroperitoneal mass, or exophytic mass from gastrointestinal origin. GISTs are <1% of all gastrointestinal malignancies (3). Duodenal GISTs constitute 4.5% of all GISTs (4). It was first found that GISTs originate from the interstitial cell of Cajal which are located in the myenteric and submucosal plexus of the gastrointestinal tract but it is now attributed to multipotential mesenchymal stem cell (19).

In the past, GISTs, leiomyoma, and leiomyosarcoma were considered as the same entity because GISTs also possessed smooth muscle features under light microscopy but now with the advancement in diagnostic modalities, it is revealed that GISTs are CD 34 immunoreactive and express tyrosine kinase c-KIT (CD 117) receptor activity (7).

The cause of GISTs is mutation in either KIT or PDGFR-α (Platelet-derived growth factor receptor α) gene (9–11). The annual incidence of GISTs is 10–20 per million per year with a 20%–30% possibility of malignancy. GISTs are more common above the age of 50 years with a median age range of 55–65 years. Some of the studies show same gender distribution but most of the studies show male predominance (20).

The commonest site of occurrence of GISTs is the stomach (50%–60%). Other sites are the small intestine (30%–40%), duodenum (4.5%), and 5% in the colon, rectum, and esophagus. Other rare sites are mesentery and omentum (9).

Seventy percent of patients with GISTs are symptomatic, 20% remain asymptomatic, and 10% are detected at autopsy. Fifty percent of patients with GIST have already been metastasized at the time of diagnosis. Microscopically, GISTs of the small intestine are more often spindled than epithelioid and are eosinophilic, composed of collagen with Periodic Acid Schiff stain positive (10).

One of the studies on the clinical analysis of primary small intestinal diseases shows the major clinical symptoms include abdominal pain (71%), abdominal mass (14%), vomiting (10%), melena (10%), and fever (10%) (11). GISTs metastasize homogeneously. Lymph node metastasis is very rare (12). The size of GISTs varies from few millimeters to more than 30 cm. Macroscopically, GISTs mostly present as an exophytic mass that is attached to the gastrointestinal tract (stomach or small intestine) in the abdominal cavity and displacing other organs (14).

Diagnostic modalities include Barium examination of the gastrointestinal tract, CT scan, and EUS guided FNAC which has 80%–85% accuracy but with considerable risk of tumor rupture and dissemination (15).

Tumor size >5 cm with extraluminal growth, irregular borders, and heterogeneous have malignant potential. Immunohistochemistry is a very important investigation that differentiates GISTs from leiomyosarcoma as GISTs are CD 117 positive in 80%–85% of cases (16).

The most important predictor of malignancy is size and mitotic rate. Tumor with size ≤2 cm and ≤5 mitosis per 50 high power field (HPF), shows low risk and good prognosis. Tumor having a size range ≥5 cm with ≥5 mitosis per 50 HPF shows high risk. Tumors of the small intestine with size >5cm are considered aggressive regardless of mitotic index. The median survival of the patient with fully resected tumor patient is 66 months and for locally advanced and metastatic tumor median, survival is 9–20 months. Two years survival after imatinib mesylate therapy is 70– 50% (17).

The most effective treatment is surgical resection with avoidance of tumor rupture because it is associated with an increased risk of peritoneal implantation. GISTs are resistant to standard chemotherapy. Imatinib mesylate is used in advanced and metastatic GISTs but the use of adjuvant imatinib therapy after complete resection of the tumor is under evaluation (18).

Stromal tumors have highly variable growth features which include tumors with intra or transmural, intraluminal, and pedunculated appearances. Clinical presentation depends on size, growth pattern as well as on the site of the tumor. Stromal tumor in the stomach has the lowest rate of acute and emergency symptoms with 31%, whereas the duodenum has 42%, followed by small bowel having acute symptoms of more than 50% (21). The intestinal tumors are found to be of high grade (70%) and high-risk prognostic group (75% and 80%) as compared to stomach GISTs (43% of highrisk prognostic group) (22).

The majority of GISTs recur in 3–5 years period. According to National Comprehensive Cancer Network Guidelines, a CT scan of the abdomen and pelvis with contrast is recommended 3–6 monthly for 3–5 years and then yearly (23).

Gastrointestinal stromal tumors can be resected surgically with its capsule being intact in order to avoid peritoneal implantations. Imatinib mesylate therapy is used for locally advanced and metastatic tumor. The prognosis of high-risk GIST is better than small intestine GIST. The recurrence rate is high, so regular follow-up is necessary.