Differentiation between Solid Pseudopapillary Neoplasm of the Pancreas and Nonfunctional Pancreatic Neuroendocrine Neoplasm Using Endoscopic Ultrasound

Objectives We investigated the utility of endoscopic ultrasound (EUS) for differentiating between solid pseudopapillary neoplasm of the pancreas (SPN) and pancreatic neuroendocrine neoplasm (PanNEN). Methods A retrospective analysis was performed on 29 and 77 consecutive patients with pathologically proven SPN and nonfunctional PanNEN. In patients who underwent contrast-enhanced harmonic EUS (CH-EUS), lesions were classified into 3 vascular patterns (hypoechoic/isoechoic/hyperechoic), and the presence of "the alveolus nest sign,"which we previously reported as a characteristic feature of SPN on CH-EUS, was also assessed. Results Conventional EUS findings showed that calcification echoes were significantly more frequent in SPN lesions than in PanNEN lesions (19/29 [66%] vs 21/77 [27%], P = 0.001) as was internal isoechogenicity or hyperechogenicity (10/29 [34%] vs 11/77 [14%], P = 0.029). Contrast-enhanced harmonic EUS findings showed that SPN lesions more frequently had the isoechoic or hypoechoic vascular pattern, and significantly more frequently had the alveolus nest sign (18/25 [72%] vs 4/60 [7%], P < 0.001). In a multivariate analysis, the presence of the alveolus nest sign contributed the most to the SPN diagnosis (odds ratio, 70; 95% confidence interval, 6.2-786). Conclusions Endoscopic ultrasound, particularly the presence of the alveolus nest sign on CH-EUS, is useful for differentiating SPN from PanNEN.