Endocrine tumours, which arise from the islet cells in the pancreas, include insulinomas, which are benign, and gastrinomas, which are more often malignant. They are usually hypoechoic, welldefined and exhibit a mass effect, often with a distally dilated main pancreatic duct. They are generally smaller at presentation than adenocarcinomas, and tend to arise in the body or tail of pancreas. Up to 40% of these tumours go undetected by both transabdominal ultrasound and CT, with endoscopic ultrasound and laparoscopic ultrasound having the highest detection rates for insulinomas.
Gastrinomas tend to be multiple and may also be extrapancreatic. A small proportion of pancreatic cancers contain an obvious fluid content. Cystadenocarcinomas, which produce mucin, are similar in acoustic appearance to a pseudocyst, but unlike a pseudocyst, a mucinous neoplasm is not associated with a history of pancreatitis.
It is also possible within a lesion to see areas of haemorrhage or necrosis which look complex or fluid-filled. Calcification is also seen occasionally
within pancreatic carcinomas. The adenocarcinoma is vascular and highvelocity arterial flow may be identified within it in many cases (Fig. 1,2).
The pancreatic duct distal to the mass may be dilated. It may, in fact, be so dilated that it can be initially mistaken for the splenic vein. The walls of
the duct, however, are usually more irregular than the smooth, continuous walls of the splenic vein.
Colour Doppler is useful in confirming the lack of flow in the duct and in identifying the vein behind it (Fig. 3,4).