Endoscopic ultrasound in the detection of pancreatic islet cell tumours

Abstract

The role of endoscopic ultrasound (EUS) in the detection of pancreatic islet cell tumours is reviewed. Functioning islet cell tumours are frequently small at presentation (90%< 2 cm). Advances in cross-sectional imaging with CT and MRI have resulted in improved detection rates of these small lesions. The sensitivity of EUS in the detection of insulinoma is similar to helical or multislice CT, i.e. between 82 and 94%, while a combination of both techniques is reported to identify 100% of tumours. EUS may be considered a primary diagnostic tool in these patients. EUS has a secondary role in the detection of gastrinomas as over 50% are malignant and 5% extra-pancreatic in position. CT should be used as a first-line investigation. EUS is valuable in problem solving in these patients. EUS has a role in staging large tumours prior to surgery. EUS-guided fine needle aspiration may provide cytological confirmation of the nature of a tumour prior to surgery.

Figure 1

(a) Typical EUS appearance of insulinoma: a well defined hypoechoic 1.5 mm mass in the mid body of the pancreas. (b) Two very small insulinomas (arrowed) measuring less than 5 mm in the distal pancreas.

Figure 2

(a) Isoechoic insulinoma in the pancreatic head (arrowed). (b) Pedunculated insulinoma (Tu) arising from the uncinate process (UN). SMV, superior mesenteric vein.

Figure 3

The value of multiphase CT contrast-enhanced imaging in the detection of insulinomas. (a) Twenty-five seconds post contrast, two small hyperattenuating lesions are observed in the head of the pancreas (arrowed). (b) At 40 s there is optimal visualisation of both lesions. (c) At 65 s only one lesion is identified; the second has become isoattenuating.

Figure 4

‘Gastrinoma triangle’. Tumour arises in the pancreatic head, duodenal wall or in the peri-pancreatic tissues.

Figure 5

(a) A well defined mass (Tn) of mid echogenicity seen lateral to the head of the pancreas on EUS in a patient with biochemical evidence of Zollinger–Ellison syndrome. (b, c) CT scans in 91 and 92 had failed to detect the tumour (T) but on repeat scanning (d) the lesion was clearly seen in the duodenal wall on a reconstructed sagittal view.

Figure 6

(a) Small superficial gastric carcinoid tumour (arrow). (b) Large centrally cystic malignant gastric carcinoid.

Figure 7

(a) CT scan of pancreas reported as normal in a patient with biochemical evidence of a gastrinoma. (b, c) EUS demonstrates two small tumour nodules inferior to pancreatic head. (d, e) Review of the CT reveals two small enhancing nodules corresponding to the EUS appearance. Histology reveals two foci of malignant gastrinoma in peri-pancreatic nodes.

Figure 8

(a) Non-functioning islet cell tumour with peripheral calcification. (b) Cystic change within an insulinoma.

Figure 9

Irregular peripheral margins in a malignant insulinoma.

Figure 10

(a) Endoscope positioned in the stomach for transgastric wall puncture of a small pancreatic mass. (b) Needle tip (arrow) visualised within the mass.