It is located behind the superior mesenteric artery and superior mesenteric vein, in front of the inferior vena cava and above the horizontal part of the duodenum, which is relatively hidden in medical imaging and can be easily confused with the horizontal part of the duodenum and misdiagnosed. If malignant tumor appears in this area, it is very easy to metastasize to peritoneum and adjacent organs and tissues through blood vessels because it is adjacent to superior mesenteric artery, superior mesenteric vein and inferior vena cava, and there is no obvious discomfort symptom in early stage of disease onset, but metastasis to adjacent organs and tissues has already appeared when it is discovered, and the disease develops rapidly, so it is very difficult to treat surgically and the effect is poor.