A gastrointestinal stromal tumor of the duodenum masquerading as a pancreatic head tumor

Figure 1 Duodenal endoscopy neither showed an intraluminal mass nor a mucosal abnormality under good visualization to the fourth part of the duodenum.

Figure 2 Abdominal ultrasound showed 2. 3 cm sized, oval-shaped hypoechoic solid nodule around the uncinate process of the pancreas (arrow).

Figure 3 The CT scan of upper abdomen showed an intense homogenously enhancing tumor with 2. 3 cm in diameter in the pancreatic head region (arrow).

Figure 4 Macroscopic appearance of the resected specimens; a round yellow gray colored tumor of cut surface (arrows) indicated the submucosal mass growing outwards towards the duodenal lumen.

Figure 5 A well-defined subserosal duodenal GIST showing interlacing fascicles of the spindle cells with elongated cytoplasm (H&E stain; A: × 20, B: × 200).

Figure 6 The tumor cells react positively for CD34 (A: × 200) and c-kit (B: × 200) while negative for SMA (C: × 100) on immunohistochemistry.