Clinical role of contrast-enhanced harmonic endoscopic ultrasound in differentiating pancreatic solid lesions

Accurate diagnosis of pancreatic solid lesions is often difficult using conventional imaging modalities. With the recent introduction of contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS), it is now possible to evaluate the microvascular environment and dynamic enhancement of a variety of pancreatic lesions. With CEH-EUS, three patterns of pancreatic lesion enhancement compared with the normal pancreatic tissue (fast, simultaneous, or slow), two washout patterns (fast or slow) and two distribution patterns (homogeneous, inhomogeneous) can be described. By evaluating the microvasculature, enhancement speed, and washout pattern, CEH-EUS may help to differentiate pancreatic adenocarcinoma from other masses and differentiate between pancreatic neuroendocrine tumor (pNET) and inflammatory masses. The finding of a hyperenhancing lesion on CEH-EUS, both with homogeneous and inhomogeneous patterns, was a strong predictor of histology different from adenocarcinoma (94% positive predictive value). pNET was the most common hyperenhancing lesions overall. Although CEH-EUS is useful for ruling out pancreatic ductal adenocarcinoma, making the differential diagnosis between pNETs and pseudotumoral pancreatic masses is difficult because both may share an isovascular or hypervascular appearance. Currently the interpretation of CEH-EUS findings is examiner-dependent. In the future, digital image analysis by image-processing techniques should allow more objective interpretation.