Difficulty in preoperative diagnosis of a patient with a neuroendocrine neoplasm of the pancreas

Abstract

A 47-year-old woman was incidentally found to have a mass in the tail of the pancreas on a contrast-enhanced CT scan. EUS-FNA was performed but the specimen was non-diagnostic and she was referred to our hospital. Contrast-enhanced CT scan showed a hypovascular mass with delayed enhancement in the periphery. Repeat EUS showed a heterogenous hypoechoic mass in B mode and contrast-enhanced EUS using Perflubutane showed poor enhancement in the central part of the mass but early contrast enhancement in the margin. Several imaging findings highly suggested the mass to be a pancreatic duct adenocarcinoma. Prompt surgery without re-biopsy was preferred and curative distal pancreatectomy performed. Pathological examination showed the mass to be a NET G2. Pathological findings of hyaline necrosis and fibrosis in the central part of the tumor also reflected the imaging findings. While typical pancreatic NET tumors are hypervascular and relatively easy to diagnose, atypical lesions with disparate imaging findings are often encountered. A NET with a reduced contrast effect is considered to be relatively high grade and the poor enhancement is generally seen in larger masses. This tumor was small but highly atypical.