Cystic pancreatic neuroendocrine tumors: To date a diagnostic challenge

Objective: Cystic PNETs are an uncommon neoplasms increasingly detected in current clinical practice which often present a diagnostic challenges to both the experienced radiologist and pathologist. The aim of this study was to review the available literature to summarize current data that compare and evaluate both the clinical and pathologic features of cystic pancreatic neuroendocrine tumors. Materials and methods: A systematic review of the current literature was performed using the search engines EMBASE and PubMed to identify all studies reporting on cystic pancreatic neuroendocrine tumors. The MeSH search terms used were "cystic pancreatic neuroendocrine tumors", "endocrine neoplasms", and "pancreatic cysts". Multiple combinations of the keywords and MeSH terms were used. Results: The clinical evaluation of cystic pancreatic lesions appears to suffer from same limitations despite the improvement in the diagnostic tools. Subsequently, we highlight diagnostic pitfalls and differential diagnosis of these cystic tumors. In this review we discuss current advances in the application of the imaging modalities and characteristics features with special emphasize on endoscopic ultrasound (EUS), and EUS guide fine needle aspiration (EUS-FNA). Conclusions: Cystic neuroendocrine tumor in the pancreas underlines the clinical impact of endoscopic ultrasound in the work-up of patients with unclear lesions in the pancreas. EUS-FNA cytology and cyst fluid analysis is a useful adjunct to abdominal imaging for the diagnosis of pancreatic cystic lesions. Due to the evident diagnostic difficulties, we hypothesize that cyst fluid characteristics, including cytomorphological features, is the most accurate test to achieve a preoperative diagnosis and to provide a basis for prognostic prediction.