Pancreatic cancer staging. Endoscopic ultrasonography criteria for vascular invasion.

Endoscopic ultrasound (EUS) is the most sensitive imaging test available for examining the pancreas and associated structures. Small (< 2 cm) pancreatic malignancies can be detected with accuracy rates of more than 90%. Several EUS criteria have been proposed for their ability to diagnose malignant venous invasion. Although obstruction of a mesenteric vein and the resulting venous collaterals is a specific sign of unresectability, it is a rather insensitive parameter. As an alternative, signs of venous wall invasion, such as "irregular wall" have been proposed as being sensitive (67%-100%) and specific (100%) for malignant invasion of mesenteric veins. EUS appears to be particularly sensitive for detecting invasion of the portal and splenic veins. In contrast, the superior mesentera veins are more difficult to image with EUS and the results of staging of pancreatic masses demonstrate poor sensitivity (12%-17%) for detecting vascular invasion of the superior mesenteric vein.