Endoscopic Ultrasound-Guided Fine-Needle Aspiration Cytology of Pancreatic Neuroendocrine Tumors.

Background: Pancreatic Neuroendocrine Tumors (PNTs) are relatively uncommon tumors that account for 1 to 2% of all pancreatic neoplasms. The aim of this report is to describe the cytomorphologic and immunocytochemical features of PNTs obtained by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) and to compare them with the histological results. Design: Forty cases diagnosed with PNTs based on EUS-FNA were studied retrospectively (from 2003 to 2010). Clinical data, EUS findings, cytological and immunocytochemical features were reviewed with particular attention to the on-site slides. The final histopathologic diagnosis from twenty-three patients was also available for comparison. Results: The case series was of 40 patients (20 men, 20 women), ranging in age from 30 years to 75 years. The mean size of the tumors by EUS was 29 mm (range, 8-100 mm). The average number of FNA per patient to obtain adequate material was 3. The most helpful cytologic findings for the diagnosis of PNTs were: i) high cellularity sample ii) monotonous, poorly cohesive population of small or medium-sized cells iii) granular chromatin (salt and pepper) and iv) plasmacytoid morphology. Immunocytochemistry (positivity for chromogranin A and/or synaptophysin) on cell blocks confirmed the neuroendocrine differentiation of tumors in all patients and Ki67 index was effective for distinguishing well differentiated from high/grade PNTs (p=0.001). The cytological diagnosis of PNT was histologically confirmed in 23 cases (57%) submitted to surgical resection Conclusions: EUS-FNA is an efficient and accurate procedure for the diagnosis of PNTs and may have a role in determining management strategy