A duodenal gastrointestinal stromal tumor mimicking a pancreatic neuroendocrine tumor: a case report

Abstract

Background: Duodenal gastrointestinal stromal tumors are rare. If tumor growth is extraluminal and involves the head of the pancreas, the diagnosis of a duodenal gastrointestinal stromal tumor is difficult.

Case presentation: A 44-year-old Japanese woman was referred to our hospital with anemia. An enhanced computed tomography scan showed a hypervascular mass 30 mm in diameter, but the origin of the tumor, either the duodenum or the head of the pancreas, was unclear. Upper gastrointestinal endoscopy revealed bulging accompanied by erosion and redness in part of the duodenal bulb. Mucosal biopsy was not diagnostic. Endoscopic ultrasound fine-needle aspiration was difficult to perform because a pulsating blood vessel was present in the region to be punctured. These findings led to a diagnosis of pancreatic neuroendocrine tumor invasion to the duodenum. The patient underwent pancreaticoduodenectomy. Histologically, the tumor was made up of spindle-shaped cells immunohistochemically positive for c-Kit and CD34. The tumor was ultimately diagnosed as a duodenal gastrointestinal stromal tumor.

Conclusion: Extraluminal duodenal gastrointestinal stromal tumors are rare and mimic pancreatic neuroendocrine tumors. Endoscopic ultrasound fine-needle aspiration is useful for preoperative diagnosis, but it is not possible in some cases. Intraoperative diagnosis based on a completely resected specimen of the tumor may be useful for modifying the surgical technique.

Keywords: Duodenal gastrointestinal stromal tumor; Fine-needle aspiration; Pancreatic neuroendocrine tumor; Pancreaticoduodenectomy.

Fig. 1

a, b CT showing a 30-mm mass heterogeneously stained at the margins, with the border between the duodenum and the head of the pancreas unclear (Arrows)

Fig. 2

PET showing tumor SUVmax of 16.7

Fig. 3

a Upper gastrointestinal endoscopy revealing bulging accompanied by erosion and redness in part of the duodenal bulb. b EUS demonstrating a 40 × 35 mm² mass with cystic and solid components in the head of the pancreas. c EUS fine-needle aspiration (FNA) considered, but was difficult to perform, because of a pulsating blood vessel present in the region to be punctured

Fig. 4

Macroscopic findings included a 4.0 × 2.3 × 3.9 cm³ mass occupying the first part of the duodenum that broke down on the mucosal surface, forming an ulcer, and developing extrusive growth toward the pancreatic head

Fig. 5

Microscopic findings included the tumor being made up of spindle-shaped cells, including nine mitotic figures per 50 high-power fields, immunohistochemically positive for vimentin, C-kit, and DOG-1. The tumor was diagnosed as a high risk dGIST on the basis of the Fletcher classification or the modified Fletcher classification