 Since its initial report in 1992, endoscopic ultrasound-guided fine needle aspiration EUS-FNA has become an increasingly important tool for the evaluation of lesions of the gastro-intestinal tract and of adjacent organs. The diagnostic accuracy of EUS-FNA ranges from 60 to 90 according to the site of investigation and it is especially low for neoplasms such as stromal tumors, lymphomas, and well-differentiated adenocarcinomas that are difficult to be diagnosed by cytology alone. Moreover, the accuracy of EUS-FNA strongly relies on rapid on-site evaluation ROSE of the adequacy of the collected specimens by a cytopathologist or a cytotechnician, who can also help in establishing the need for additional samples to perform ancillary studies that are required in some cases to reach an effective diagnosis. 